Download Final practice exam

2012Spring SI
Helena
Stat 226 Final practice exam
1. TRUE or FALSE.
T F The standard deviation for the sample mean is smaller than the standard deviation for
individual observations.
T F The range is always larger or equal to the IQR.
T F Experiments are useful methods for showing cause-and-effect relationships.
T F A z-score tells us how many means we are away from the standard deviation.
T F P[ Z < 0 ] = 0.5
T F For a skewed distribution, we should always use the mean and standard deviation as the
numeric summaries.
T F The parameter is always fixed while the statistic varies from sample to sample.
T F For a one-sided test, the p-value is affected by the direction of the alternative hypothesis.
T F The correlation coefficient for two quantitative variables is equal to zero. This implies that
there is no association between the two variables.
T F When we are more concerned about a Type II error than a Type I error we use a larger level
of significance.
T F A bar chart is used to display quantitative data.
T F If a researcher was hoping to show that the results of an experiment were statistically
significant they would prefer a smaller p-value.
T F The standard deviation of the heights of a previous 226 class was 26 inches. John was a lot
taller than the rest of the class. When he was removed from the study, the standard deviation
remained the same.
2. For this graphical display of Quiz Scores, which estimates of the mean and median are most
plausible?
2012Spring SI
Helena
(a) median = 13.0 and mean = 12.0
(b) median = 14.0 and mean = 15.0
(c) median = 16.0 and mean = 14.3
(d) median = 16.5 and mean = 16.2
3. Determine which graph has the higher standard deviation (it is not necessary to do any
calculations to answer this question.
(a) A has a larger standard deviation than B.
(b) B has a larger standard deviation than A.
(c) Both graphs have the same standard deviation.
4. Which of the following does not make sense?(Circle all that apply)
(a) r < 0.1
(b) r = 0.5
(c) r2 = <0.05
(d) r > 0.95
5. Suppose that a random sample of 41 state college students is asked to measure the length of
their right foot in centimeters. A 95% confidence interval for the mean foot length for students at
this university turns out to be (21.709, 25.091). If instead a 90% confidence interval was
calculated, how would it differ from the 95% confidence interval?
(a) The 90% confidence interval would be narrower.
(b) The 90% confidence interval would be wider.
(c) The 90% confidence interval would be the same as the 95% confidence interval.
5. A research article gives a p-value of 0.001 in the analysis section. Which definition of a pvalue is the most accurate?
(a) the probability that the observed outcome will occur again.
(b) the value that an observed outcome must reach in order to be considered significant under the
null hypothesis.
(c) the probability that the null hypothesis is true.
(d) the probability of observing an outcome as extreme or more extreme than the one observed if
the null hypothesis is true.
2012Spring SI
Helena
6. A random sample of 25 college statistics textbook prices is obtained and the mean price is
computed. To determine the probability of obtaining a more extreme mean than the one obtained
from this random sample, you would need to refer to:
(a) the population distribution of all college statistics textbook prices.
(b) the distribution of prices for this sample of college statistics textbooks.
(c) the sampling distribution of textbook prices for all samples of 25 textbooks from this
population.
7. A researcher conducts an experiment on human memory and recruits 15 people to participate
in her study. She performs the experiment and analyzes the results. She obtains a p-value of 0.17.
Which of the following is a reasonable interpretation of her results?
(a) There could be a treatment effect, but the sample size was too small to detect it.
(b) This proves that her experimental treatment has no effect on memory.
(c) She should reject the null hypothesis. There is evidence of a small effect on memory by her
experimental treatment.
8. A questionnaire concerning satisfaction with the Financial Aid on campus was mailed to 50
students on a university campus. The 50 students in this survey are an example of a _______.
9. This is a variance contest. You must give a list of eight numbers chosen from the whole
numbers 3, 4, 5, 6, 7, 8, 9 with repetitions allowed.
a. Give a list of eight numbers with the largest variance such a list can possibly have.
b. Give a list of eight numbers with the smallest variance such a list can possibly have.
10. The following data are the average temperatures (in degrees Fahrenheit) for each month in
2008 for Ames. They have been ordered from lowest to highest for your convenience. Please
use this dataset to answer the following questions.
20, 32, 35, 40, 48, 55, 60, 64, 68, 75, 84, 88
[a] Draw a stem and leaf plot for this dataset that.
[d] Using the 5-number to draw the corresponding boxplot.
2012Spring SI
Helena
11. The Otis Score (Score on the Otis test "an IQ" type test) is used nationwide, and individual
Otis Scores follow a normal distribution with a mean of 103 and a standard deviation of 18. The
corporation requires a minimal Otis score of 80 to be accepted for a job position. The highest
Otis Score of an individual the company hired is 140.
(a) What percentage of individuals nationwide score above the highest employee at this
corporation?
(b) What percentage of individuals nationwide score lower than the lowest employee at this
corporation?
(c) What range of Otis Scores do 99.7%, or nearly all individuals nationwide, fall between?
(d) The average Otis Score at the corporation is in the 65th percentile of all individuals
nationwide. What was the average Otis Score at the corporation?