In: Statistics and Probability
A sample of college students was asked how much they spent monthly on pizza. Approximate the standard deviation for the cost.
Monthly pizza cost. total number of students
10.99-19.99 7
20.99-29.99 20
30.99-39.99 23
40.99-49.99 20
50.99-59.99 5
The sample standard deviation for the cost is (round to nearest cent)
Solution:
First we will calculate mean
Mean = summation(f*Midpoints)/summation(f) = (108.43+509.8+816.27+909.8+277.45)/(7+20+23+20+5) = 2621.75/75 = 34.96
Standard deviation can be calculated as
Standard deviation = Sqrt(summation(f*(midpoints-Mean)^2)/f-1)) = Sqrt(2653.5663+1793.618+6.6407+2217.618+2107.4045)/74( = Sqrt(118.63) = 10.88