# Thread: pet statistics

1. ## 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?

2. 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).

3. 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

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

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

Is this correct?