The conditions needed for the one sample t -test are present.(from Table B; on the TI-83/84, tcdf(2.39,100,7) =0.024 ).Because P < 0.05, reject H 0 . We have evidence that, in identical twins reared apart, the better
educated twin is likely to have the higher IQ score.
a. = 123.85, s = 9.07. We are told that the 20 cans of paint have been randomly selected. It is
reasonable to assume that a sample of this size is small relative to the total population of such cans.
A boxplot of the data shows no significant departures from normality. The conditions necessary to
construct a 95% t confidence interval are present.
b. We are 95% confident that the true mean drying time for the paint is between 119.6 minutes and
128.1 minutes. Because 120 minutes is in this interval, we would not consider an average drying
time of 120 minutes for the population from which this sample was drawn to be unusual.c. (On the TI-83/84, we find P -value = 2 × tcdf(1.90,100,19) = 0.073. )
d. We know that if a two-sided α -level significance test rejects (fails to reject) a null hypothesis,