1. A substance abuse researcher wants to know whether reaction time is decreased by the use of methamphetamines . Reaction times in the general population are distributed normally with a mean of 348.4 milliseconds (msec). A sample of 12 methamphetamine users is tested. Their mean reaction time is 333.6 msec and their standard deviation equals 46.0 msec. What is the value of the lower limit of the 99% Confidence Interval for the mean reaction time of methamphetamine users? Enter value with one decimal.
2. An experiment a student set up for class focuses on the productivity of office workers when there are indoor plants present in the office environment. The researcher decides to set up a one-tailed hypothesis, but the results show the effect in the opposite direction. Can the researcher change the original hypothesis to be two-tailed? a. Yes but change cv. b. yes but it doesn't affect anything due to sig. result. c. yes because effect was meaningful. d. no, not ethical to change after fact.
3. An educational psychologist wants to test whether a new teaching method negatively affects reading comprehension scores using a significance level of 0.05. The mean reading comprehension scores of students using the old method has a value of 78.9 and are normally distributed. A sample of 101 students taught with the new method has a mean reading comprehension score of 78.6 and a standard deviation of 10.0. What is the value of the test statistic? Enter value with three decimals.