Question

Poisoning by the pesticide Dieldrin causes tremors and convulsions. In a study of Dieldrin poisoning, researchers fed several rats a measured amount of Dieldrin. They then measured electrical characteristics of the rats' nervous system that might explain how Dieldrin poisoning causes tremors. One important variable was the "absolute refractory period"—the time required for a nerve to recover after a stimulus. This period varies Normally. Measurements of the absolute refractory period, in milliseconds, for six rats were 2.2, 2.4, 2.5, 2.5, 2.6, and 2.7.

Part A: Find the mean absolute refractory period x and the standard error of the mean.

Part B: Calculate a 98% confidence interval for the mean absolute refractory period for all rats of this strain when subjected to the same treatment.

Part C: Suppose the mean absolute refractory period for unpoisoned rats is known to be 2.3 milliseconds. Dieldrin poisoning should slow nerve recovery and thus increase this period. Do the data give good evidence for this supposition? What can you conclude from a hypothesis test? Justify your response with statistical reasoning.

Answer 1

A)

mean =2.4833

sample size             n=	6.00
sample std deviation s=	0.172
std error sx=s/√n=	0.0703

b)

for 98% CI; and 5 df, critical t=		3.3650
margin of error E=t*std error                            =		0.237
lower bound=sample mean-E =		2.247
Upper bound=sample mean+E=		2.720
from above 98% confidence interval for population mean =(2.247 , 2.720 )

c)

since our confidence interval contains 2.3 as a plausible value of population mean,

we can not conclude that Dieldrin poisoning should slow nerve recovery and thus increase this period.