Question

In: Statistics and Probability

There are researchers who want to know if M poisoning in mice is less extreme in...

There are researchers who want to know if M poisoning in mice is less extreme in males. An SRS of one hundred male mice and an independent SRS of one hundred female mice are obtained. The male mice had a sample mean of thirty-nine and a sample standard deviation of eight. The female mice had a sample mean and standard deviation of 40 and 10, respectively. Let u1 represent the true mean response for the males and u2 represent the true mean response of the females.

a) You must find a point estimate for the difference that there is between the two population means.

b) Find a ninety-nine percent confidence interval for u1-u2 and explain your results.

Solutions

Expert Solution

a)

Point estimate of difference = 39 - 40 = -1

b)

SE = sqrt[ (s12/n1) + (s22/n2) ]              
(s12/n1)   0.6400          
(s22/n2)    1.0000          
SE   1.2806          
              
DF = (s12/n1 + s22/n2)2 / { [ (s12 / n1)2 / (n1 - 1) ] + [ (s22 / n2)2 / (n2 - 1) ] }              
[ (s12 / n1)2 / (n1 - 1) ]            0.004  
[ (s22 / n2)2 / (n2 - 1) ]           0.01  
(s12/n1 + s22/n2)2           2.69  
DF =    189          


t value at 99% = 2.602

CI = (x1- x2) +/- t *sqrt(s1^2/n1+s2^2/n2)
= ( 39 -40) +/ 2.602 *sqrt(8^2/100 + 10^2/100)
= (-4.3325 , 2.3325 )


The 99% CI is (-4.3325 , 2.3325 )


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