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Natural Resources 340

Natural Resources 340 - Biological Statistics I Homework 2...

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Biological Statistics I Biometry 301 / Natural Resources 313 Homework 2 Name: Jackie Lewis Section: 1 Date: 9-5-07 1. (5 points) One useful method for examining data is to plot the distribution of the data for various factors, such as gender. Use the command below to create a boxplot that compares head size between females and males for the measured samples taken from the class: boxplot( Class07$head[Class07$sex=="F"], Class07$head[Class07$sex=="M"], ylab="Head Size (cm)", names=c("Female","Male")) 55 60 65 Female Male Head Size (cm)
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Which group appears to have bigger heads on average? Males tapply(Class07$head, Class07$sex, mean) F M 56.21053 58.54762 The difference between the two values is 2.337 What is the difference in mean head size between males and females? Males: The tapply() command, which applies a function such as mean() to the first column based on categories in the second column, may help in sorting this out: tapply(Class07$head,Class07$sex,mean) Modify the tapply() command to examine the median, range, and quantiles (i.e. quantile). On the boxplot figure pencil in the appropriate parts of the box with values corresponding to the maximum, 75th percentile, 50 th percentile, 25th percentile and minimum for both males and fe males. Finally, write in the location of the mean of each group.
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