test 2

Question 1

how to solve this problem:

Find the fraction of smokers and nonsmokers with weights beyond 1σ and 2σ from the mean.

Answer 1

1. calculate standard deviation:

sd.smoke <- sd(cdc[smoke100==1,]$weight)

2. calculate mean:

mean.smoke <- mean(cdc[smoke100==1,]$weight)

3. find threshold values for beyond mean:

mean.smoke + sd.smoke

4. calculate the number of people beyond the threshold and find the proportion:

sum(weight[smoke100==1] > mean.smoke + sd.smoke)/sum(smoke100==1)

for proportions you divide by the total amount

• this is also only for smokers but you have to repeat for nonsmokers