Question

Researchers want to estimate the difference between height of two counties. For this, a sample of 35 people from county A and a sample of 42 people from county B are taken. County A has mean height 5.75 ft and sample standard deviation 0.46 and County B has 5.25 ft. and sample standard deviation 0.21. Find the pooled variance.

0.120
	0.245
	0.421
	0.346
	0.061

Answer 1

Sample #1   ---->   1
mean of sample 1,    x̅1=   5.750
standard deviation of sample 1,   s1 =    0.460
size of sample 1,    n1=   35
      
Sample #2   ---->   2
mean of sample 2,    x̅2=   5.250
standard deviation of sample 2,   s2 =    0.210
size of sample 2,    n2=   42

pooled variance , Sp²=   ([(n1 - 1)s1² + (n2 - 1)s2²]/(n1+n2-2)) = 0.120 (answer)