Predation by house cats, Felis catus (L.), in Canberra, Australia. II. Factors affecting the amount of prey caught and estimates of the impact on wildlife

1998 ◽  
Vol 25 (5) ◽  
pp. 475 ◽  
Author(s):  
D. G. Barratt
Keyword(s):  
Significant Influence ◽  
Felis Catus ◽  
Potential Prey ◽  
Sample Mean ◽  
Sample Median ◽  
Factors Affecting ◽  
Source Areas ◽  
Residential Developments ◽  
The Mean ◽  
The Impact

Information on the amount of vertebrate prey caught by house cats in Canberra was collected by recording prey deposited at cat owners’ residences over 12 months. The amount of prey taken was not significantly influenced by cat gender, age when neutered, or cat breed. Nor did belling or the number of meals provided per day have a significant influence on the amount of prey caught. The age of the cat and the proportion of nights spent outside explained approximately 11% of the variation in the amount of prey caught by individual cats. In all, 43% of variation in predation on introduced species (predominantly rodents) was explained by distance from potential prey source areas (i.e. rural/grassland habitat) and cat density. The mean number of prey reported per cat over 12 months (10.2) was significantly lower than mean predation per cat per year based on estimates made by cat owners before the prey survey began (23.3). Counts of the amount of prey caught by house cats were highly positively skewed. In all, 70% of cats were observed to catch less than 10 prey over 12 months, but for 6% of cats, more than 50 prey were recorded. Estimates of predation by house cats, particularly extrapolated estimates, should be treated with caution. The total number of prey caught by house cats in Canberra estimated using the sample median was approximately half the estimate based on the sample mean. Predation estimates alone do not prove that prey populations are detrimentally affected, especially in highly disturbed and modified environments such as suburbs. Impacts on native fauna are likely to be most significant in undisturbed habitat adjacent to new residential developments.

scholarly journals Analyzing the Effect of the Senior Management’s Support on the Relationship between Factors Affecting and Employees’ Performance in the Al-Zawiya University of Libya

2017 ◽  
Vol 13 (3) ◽  
pp. 42
Author(s):  
Nasreddin Ramadhan Dukhan ◽  
Norhisham Mohamad ◽  
Asbi B Ali
Keyword(s):  
Likert Scale ◽  
Factors Affecting ◽  
The Mean ◽  
Multiple Groups ◽  
Strongly Agree ◽  
The Impact ◽  
The Relationship ◽  
Variable Performance

This study aims to test the influence of the senior management’s support as a moderating variable on the relationship between the independent factors (Training, Empowerment, Motivation and Communication) and the dependent variable (Performance of Employees). (SEM-AMOS) is used to test the impact of the moderating variable. Where it is depended on the method of sampling or analysis of what is known as multiple-groups analysis. The paragraphs of the senior management’s support variable are collected and divided into two groups according to the mean of the total paragraphs. In addition, according to the relative weights given to the paragraphs of the questionnaire, using a five- point’s Likert scale: 1= strongly disagree to 5 = strongly agree. The first group consisted of the grades less than the mean and it is considered as the group which is non-supporters of the existence of support. While the second group consisted of the grades higher than the mean and considered as the group which is a supporter of the existence of support. The study found that the model of study in the presence of the support of the senior management’s is appropriate for the second group and inappropriate in light of the lack of support by the senior management’s support for the first group.

scholarly journals Factors Affecting Hemodialysis Patients' Satisfaction with Their Dialysis Therapy

2010 ◽  
Vol 2010 ◽  
pp. 1-5 ◽  
Author(s):  
M. Al Eissa ◽  
M. Al Sulaiman ◽  
M. Jondeby ◽  
A. Karkar ◽  
M. Barahmein ◽  
...  
Keyword(s):  
Social Life ◽  
Demographic Data ◽  
Standard Of Care ◽  
Hemodialysis Patients ◽  
Sexual Life ◽  
Dialysis Therapy ◽  
Factors Affecting ◽  
Degree Of Satisfaction ◽  
The Mean ◽  
The Impact

Aim. To assess the degree of satisfaction among hemodialysis patients and the factors influencing this satisfaction.Methods. Patients were recruited from 3 Saudi dialysis centers. Demographic data was collected. Using 1 to 10 Likert scale, the patients were asked to rate theoverall satisfactionwith, andthe overall impactof, their dialysis therapy on their lives and to rate the effect of the dialysis therapy on 15 qualities of life domains.Results. 322 patients were recruited (72.6% of the total eligible patients). The mean age was 51.7 years (15.4); 58% have been on dialysis for 3 years. The mean Charlson Comorbidity Index was 3.2 (2), and Kt/V was 1.3 (0.44). The mean satisfaction score was (7.41 2.75) and the mean score of the impact of the dialysis on the patients' lives was 5.32 2.55. Male patients reported worse effect of dialysis on family life, social life, energy, and appetite. Longer period since the commencement of dialysis was associated with adverse effect on finances and energy. Lower level of education was associated with worse dialysis effect on stress, overall health, sexual life, hobbies, and exercise ability.Conclusion. The level of satisfaction is affected by gender, duration on dialysis, educational level, and standard of care given.

scholarly journals The Impact of Superficial Vessel Density on Glaucoma Progression according to the Stage of Glaucoma

2021 ◽  
Vol 10 (21) ◽  
pp. 5150
Author(s):  
Jiyun Lee ◽  
Chan Kee Park ◽  
Hae-Young Lopilly Park
Keyword(s):  
Longitudinal Study ◽  
Vessel Density ◽  
Mean Deviation ◽  
Progression Rate ◽  
Factors Affecting ◽  
Potential Marker ◽  
Rate Of Progression ◽  
Advanced Glaucoma ◽  
The Mean ◽  
The Impact

Purpose: To investigate the clinical significance of vessel density (VD) on visual field (VF) progression regarding the severity of glaucoma. Methods: A total of 130 eyes were recruited in this retrospective and longitudinal study. Superficial and deep VDs in circumpapillary and macular regions were measured via ImageJ. The rate of VF progression was defined as the mean deviation (MD) slope (dB/year). Linear regression was used to verify factors affecting deterioration of VF. The eyes with lower superficial VD were further analyzed. Results: Fifty patients with early glaucoma (EG) (MD > −6 dB) and 52 patients with moderate-to-advanced glaucoma (MAG) (MD ≤ −6 dB) were included. A faster progression rate was found in MAG (p = 0.049). Superficial VD was noticeably related to the VF progression rate in total eyes and in MAG (Both Ps ≤ 0.007, respectively). With patients in the lower half of the superficial VD, the VD was significantly associated with the rate of progression (B, 0.049, p = 0.021). This association was independent of the baseline MD and OCT parameters. Conclusion: Decreased superficial VD might conversely affect the progression of glaucoma even in MAG, which suggests superficial VD could be used as a potential marker to foresee the disease progression even in progressed eyes.

Wastage of conserved fodder when feeding livestock

2010 ◽  
Vol 50 (6) ◽  
pp. 400 ◽  
Author(s):  
C. R. Stockdale
Keyword(s):  
Beef Cattle ◽  
Dairy Cattle ◽  
Present Review ◽  
Factors Affecting ◽  
Storage Method ◽  
The Mean ◽  
Main Factors ◽  
Wet Weather ◽  
The Cost ◽  
The Impact

The objective of the present review was to establish levels of conserved fodder wastage when feeding livestock (sheep, beef cattle, dairy cattle) under various conditions and using various feed-out systems, and to determine the factors affecting wastage. The mean wastage of hay recorded in the literature reviewed was 17% of the DM offered, but the range was from 4 to 77%. The main factors affecting the degree of wastage were storage method, packaging method, method of feeding out, amount of fodder on offer and its palatability and/or quality and the impact of wet weather. Although the emphasis was on hay, the principles should also apply to silage. If wastage was 40% rather than 5%, the cost of feeding conserved fodder to livestock would be a third greater than producers might expect or budget on.

scholarly journals Reaction times and other skewed distributions: problems with the mean and the median

2019 ◽  
Author(s):  
Guillaume A Rousselet ◽  
Rand R. Wilcox
Keyword(s):  
Reaction Times ◽  
Small Sample ◽  
Careful Examination ◽  
Shift Function ◽  
Central Tendency ◽  
Skewed Distributions ◽  
Experimental Conditions ◽  
Sample Mean ◽  
Sample Median ◽  
The Mean

To summarise skewed (asymmetric) distributions, such as reaction times, typically the mean or the median are used as measures of central tendency. Using the mean might seem surprising, given that it provides a poor measure of central tendency for skewed distributions, whereas the median provides a better indication of the location of the bulk of the observations. However, the sample median is biased: with small sample sizes, it tends to overestimate the population median. This is not the case for the mean. Based on this observation, Miller (1988) concluded that ”sample medians must not be used to compare reaction times across experimental conditions when there are unequal numbers of trials in the conditions.” Here we replicate and extend Miller (1988), and demonstrate that his conclusion was ill-advised for several reasons. First, the median’s bias can be corrected using a percentile bootstrap bias correction. Second, a careful examination of the sampling distributions reveals that the sample median is median unbiased, whereas the mean is median biased when dealing with skewed distributions. That is, on average the sample mean estimates the population mean, but typically this is not the case. In addition, simulations of false and true positives in various situations show that no method dominates. Crucially, neither the mean nor the median are sufficient or even necessary to compare skewed distributions. Different questions require different methods and it would be unwise to use the mean or the median in all situations. Better tools are available to get a deeper understanding of how distributions differ: we illustrate the hierarchical shift function, a powerful alternative that relies on quantile estimation. All the code and data to reproduce the figures and analyses in the article are available online.

scholarly journals Estimating the sample mean and standard deviation from commonly reported quantiles in meta-analysis

2020 ◽  
Vol 29 (9) ◽  
pp. 2520-2537 ◽  
Author(s):  
Sean McGrath ◽  
XiaoFei Zhao ◽  
Russell Steele ◽  
Brett D. Thombs ◽  
Andrea Benedetti ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Meta Analysis ◽  
Outcome Variable ◽  
Sample Mean ◽  
Sample Median ◽  
Common Effect ◽  
The Mean ◽  
Novel Approaches ◽  
Summary Data ◽  
Better Than

Researchers increasingly use meta-analysis to synthesize the results of several studies in order to estimate a common effect. When the outcome variable is continuous, standard meta-analytic approaches assume that the primary studies report the sample mean and standard deviation of the outcome. However, when the outcome is skewed, authors sometimes summarize the data by reporting the sample median and one or both of (i) the minimum and maximum values and (ii) the first and third quartiles, but do not report the mean or standard deviation. To include these studies in meta-analysis, several methods have been developed to estimate the sample mean and standard deviation from the reported summary data. A major limitation of these widely used methods is that they assume that the outcome distribution is normal, which is unlikely to be tenable for studies reporting medians. We propose two novel approaches to estimate the sample mean and standard deviation when data are suspected to be non-normal. Our simulation results and empirical assessments show that the proposed methods often perform better than the existing methods when applied to non-normal data.

scholarly journals Reaction Times and other Skewed Distributions

2020 ◽  
Vol 4 ◽  
Author(s):  
Guillaume A Rousselet ◽  
Rand R Wilcox
Keyword(s):  
Reaction Times ◽  
Small Sample ◽  
Careful Examination ◽  
Shift Function ◽  
Central Tendency ◽  
Skewed Distributions ◽  
Experimental Conditions ◽  
Sample Mean ◽  
Sample Median ◽  
The Mean

To summarise skewed (asymmetric) distributions, such as reaction times, typically the mean or the median are used as measures of central tendency. Using the mean might seem surprising, given that it provides a poor measure of central tendency for skewed distributions, whereas the median provides a better indication of the location of the bulk of the observations. However, the sample median is biased: with small sample sizes, it tends to overestimate the population median. This is not the case for the mean. Based on this observation, Miller (1988) concluded that "sample medians must not be used to compare reaction times across experimental conditions when there are unequal numbers of trials in the conditions". Here we replicate and extend Miller (1988), and demonstrate that his conclusion was ill-advised for several reasons. First, the median's bias can be corrected using a percentile bootstrap bias correction. Second, a careful examination of the sampling distributions reveals that the sample median is median unbiased, whereas the mean is median biased when dealing with skewed distributions. That is, on average the sample mean estimates the population mean, but typically this is not the case. In addition, simulations of false and true positives in various situations show that no method dominates. Crucially, neither the mean nor the median are sufficient or even necessary to compare skewed distributions. Different questions require different methods and it would be unwise to use the mean or the median in all situations. Better tools are available to get a deeper understanding of how distributions differ: we illustrate the hierarchical shift function, a powerful alternative that relies on quantile estimation. All the code and data to reproduce the figures and analyses in the article are available online.

scholarly journals Factors Affecting Birth Weight And Growth Rate In Friesian X Bunaji Calves

2021 ◽  
Vol 19 ◽  
pp. 101-106
Author(s):  
O. W. Ehoche ◽  
A. E. O. Malau-aduli ◽  
B. Y. Abubakar
Keyword(s):  
Growth Rate ◽  
Body Weight ◽  
Birth Weight ◽  
Significant Influence ◽  
Season Of Birth ◽  
Correction Factors ◽  
Wet Season ◽  
Factors Affecting ◽  
Body Weights ◽  
The Mean

Calving records from 1984 - 1989 were studied to determine the influence of rearing method, sex of calf, season of birth, dam breed and year of birth on body weight at birth, 3,6 and 12 months of age in Friesian x Bunaji calves. The mean weights of calves at birth, 3, 6 and 12 months of age were 22.0, 68.2, 96.7 and 137.4 kg, respectively. Sex of calf had a significant effect, with male calves being heavier than the females by 1.2, 5.9 and 9.7 kg at birth, 3 and 6 months of age respectively. The effect of season of birth on calf body weights was not significant except at 6 months of age, when calves born during the wet season were heavier (P<0.01) than those born in the harmattan period by 9.5 kg. Year of birth had a highly significant effect (P<0.01) on calf weights from birth to yearling. Method of rearing and dam breed had no significant influence on all the weights. The results suggest the need to develop correction factors for standardisation of weight records when comparing dams on the basis of body weights of their calves.

scholarly journals Reaction times and other skewed distributions: problems with the mean and the median

2018 ◽  
Author(s):  
Guillaume A. Rousselet ◽  
Rand R. Wilcox
Keyword(s):  
Reaction Times ◽  
Small Sample ◽  
Careful Examination ◽  
Central Tendency ◽  
Skewed Distributions ◽  
Experimental Conditions ◽  
Sample Mean ◽  
Sample Median ◽  
The Mean ◽  
Small Sample Sizes

ABSTRACTTo summarise skewed (asymmetric) distributions, such as reaction times, typically the mean or the median are used as measures of central tendency. Using the mean might seem surprising, given that it provides a poor measure of central tendency for skewed distributions, whereas the median provides a better indication of the location of the bulk of the observations. However, the sample median is biased: with small sample sizes, it tends to overestimate the population median. This is not the case for the mean. Based on this observation, Miller (1988) concluded that “sample medians must not be used to compare reaction times across experimental conditions when there are unequal numbers of trials in the conditions.” Here we replicate and extend Miller (1988), and demonstrate that his conclusion was ill-advised for several reasons. First, the median’s bias can be corrected using a percentile bootstrap bias correction. Second, a careful examination of the sampling distributions reveals that the sample median is median unbiased, whereas the mean is median biased when dealing with skewed distributions. That is, on average the sample mean estimates the population mean, but typically this is not the case. In addition, simulations of false and true positives in various situations show that no method dominates. Crucially, neither the mean nor the median are sufficient or even necessary to compare skewed distributions. Different questions require different methods and it would be unwise to use the mean or the median in all situations. Better tools are available to get a deeper understanding of how distributions differ: we illustrate a powerful alternative that relies on quantile estimation. All the code and data to reproduce the figures and analyses in the article are available online.

Asteroid and Comet Impact Speeds upon Mars: Significance for Panspermia and the Supply of Organics

1997 ◽  
Vol 161 ◽  
pp. 197-201 ◽  
Author(s):  
Duncan Steel
Keyword(s):  
Probability Distributions ◽  
Regions Of Interest ◽  
Significant Fraction ◽  
Organic Chemicals ◽  
Impact Speed ◽  
The Mean ◽  
The Impact

AbstractWhilst lithopanspermia depends upon massive impacts occurring at a speed above some limit, the intact delivery of organic chemicals or other volatiles to a planet requires the impact speed to be below some other limit such that a significant fraction of that material escapes destruction. Thus the two opposite ends of the impact speed distributions are the regions of interest in the bioastronomical context, whereas much modelling work on impacts delivers, or makes use of, only the mean speed. Here the probability distributions of impact speeds upon Mars are calculated for (i) the orbital distribution of known asteroids; and (ii) the expected distribution of near-parabolic cometary orbits. It is found that cometary impacts are far more likely to eject rocks from Mars (over 99 percent of the cometary impacts are at speeds above 20 km/sec, but at most 5 percent of the asteroidal impacts); paradoxically, the objects impacting at speeds low enough to make organic/volatile survival possible (the asteroids) are those which are depleted in such species.

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