# pet statistics

• Apr 10th 2009, 07:43 PM
laser
pet statistics
Students in a class were asked to report the number of pets of their family

# pets frequency
1 3
2 19
3 16
4 9
47

I figured the frequencies from the data provided but how do you calculate the sample mean and sample standard deviation?
• Apr 10th 2009, 10:40 PM
mr fantastic
Quote:

Originally Posted by laser
Students in a class were asked to report the number of pets of their family

# pets frequency
1 3
2 19
3 16
4 9
47

I figured the frequencies from the data provided but how do you calculate the sample mean and sample standard deviation?

To calculate sample mean from a frequency table, read The Sample Mean

To calculate sample variance from a frequency table read Learning Resources: Statistics: Power from Data! Variance and standard deviation (go down about half way).
• Apr 11th 2009, 11:07 AM
laser
Thank you for the information. If I interpreted it correctly, I believe the mean is 125/47.

1*3+2*19+3*16+4*19=125
mean=125/47

I don't think I got the standard deviation right

$\displaystyle [(1-125/47)^{2}*(3/47)]+[(2-125/47)^{2}*(19/47)]$$\displaystyle +[(3-125/47)^{2}*(16/47)]+[(4-125/47)^{2}*(9/47)]=1624/2209$

1624/2209=0.73517
SD=$\displaystyle \sqrt{0.73517}=$0.85740

Is this correct?