Construct a 95% con dence interval for the di erence between the mean lifetimes oftwo kinds of light bulbs, given that a random sample of 100 light bulbs of the rst kindlasted on the average 400 hours of continuous use and 100 light bulbs of the second kindlasted on the average 420 hours of continuous use. The population standard deviations areknown to be1

On a certain portion of an experiment, a statistical test result yielded a p-value of 0.21. what can you conclude? 2(0.21) = 0.42 < 0.5; the test is not statistically significant. if the null hypothesis is true, one could expect to get a test statistic at least as extreme as that observed 21% of the time, so the test is not statistically significant. 0.21 > 0.05; the test is statistically significant. if the null hypothesis is true, one could expect to get a test statistic at least as extreme as that observed 79% of the time, so the test is not statistically significant. p = 1 - 0.21 = 0.79 > 0.05; the test is statistically significant.