DDT is a pesticide banned in the United States for its danger to humans and anim

Question

DDT is a pesticide banned in the United States for its danger to humans and animals. In an experiment on the impact of DDT, six rats were exposed to DDT poisoning and six rats were not. For each rat in the experiment, a measurement of nerve sensitivity was recorded. The researchers suspected that the mean nerve sensitivity for rats exposed to DDT is greater than that for rats not poisoned. The data follow:

Let mu(1) be the mean nerve sensitivity for rats poisoned with DDT. Let mu(2) be the mean nerve sensitivity for rats not poisoned with DDT.

Reference: Ref 17-4

The numerical value of the standard error of the difference in sample means is

Select one:

a. 9.02.

b. 1.30.

c. 4.05.

d. 2.71.

Poisoned rats: 12.207 16.869 25.050 22.429 8.456 20.589 Unpoisoned rats: 11.074 9.686 12.064 9.351 8.182 6.642

Explanation / Answer

              
Calculating the standard deviations of each group,              
              
s1 =    6.36650953          
s2 =    1.950059324          
              
Thus, the standard error of their difference is, by using sD = sqrt(s1^2/n1 + s2^2/n2):              
              
n1 = sample size of group 1 =    6          
n2 = sample size of group 2 =    6          
Thus, df = n1 + n2 - 2 =    10          

Therefore , sD =    2.71 [ANSWER, D]

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