Biostats SDS 328M Homework 5 Write your answers onto one or more separate sheets of paper. Clearly mark each sheet with your name and your lab time.
Biostats SDS 328M Homework 5
Write your answers onto one or more separate sheets of paper. Clearly mark each sheet with your
name and your lab time.
Round all answers to at least 3 decimal places and assume, unless otherwise noted, that α=0.05
1. To determine how talking on a cell phone affects driving ability, a researcher set up an
experiment where she measured the reaction times (in milliseconds) of a sample of 12 adults
under two conditions. Each participant was measured in a driving simulator while talking on a
cell phone and then again without distraction. The order was randomized, and the results are
Talking on cell 1
543 Participant No.
531 537 467 525
580 559 554 626 9
679 a. You want to use these data to test if cell phone use increases reaction time, on average.
Before you answer this question, create a boxplot to check whether the relevant
normality assumption for this analysis is met, and comment on your finding. (4pt)
b. Run a hypothesis test to answer your research question. Show all of your work and
include all steps for full credit. (4pt)
c. List at least one possible confounding variable in this study. (1pt)
2. An industrial plant dumps its waste into a nearby river, but claims that it is not impacting the
native fish that live in the river. You have measured the calcium concentration from a random
sample of 18 locations in the river and calculated a mean of 97.4 mg/L, with a standard
deviation of 4.1 mg/L. The fish are able to tolerate calcium concentrations up to 95 mg/L.
a. Assuming a normal distribution, calculate a 95% confidence interval for the mean
calcium concentration in the river. (3pts)
b. Do your data suggest that the fish are being negatively impacted? Explain your answer.
c. Assuming that you held everything else constant, how would the width of the
confidence interval change if you doubled your sample size from 18 to 36? Would it
become wider, narrower, or stay the same? (1pt) Copyright © 2016 Dept. of Statistics and Data Sciences, UT Austin 3. A study was conducted to compare the resting pulse rate among smokers and non-smokers. The
data are summarized in the table below. The pulse rate distribution in each group can be
assumed to be normal, and equal population variances can be assumed in the two groups.
Non-smokers Resting pulse rate (bpm)
3.2 Conduct the appropriate test to see if the mean resting pulse rate for smokers is higher than that
for non-smokers. Show all work and include all steps (hypotheses, rejection region, p-value,
decision and conclusion) for full credit. (5pt) Copyright © 2016 Dept. of Statistics and Data Sciences, UT Austin