Download Practice Exam Worksheet 2

Math 243 Worksheet 3
Name:)_____________________________________________
1.) Suppose that IQ scores are normally distributed with a mean of 100 and a standard deviation of 15
points.
a.) What percentile is a person in who scores an 88 on the IQ exam?
b.) What percentile is a person in who scores a 130 on the IQ exam?
c.) What score is needed to be in the top 5% of the population?
d.) What is the probability of randomly selecting a group of 9 individuals that have an average IQ score
of 109 points?
e.) A researcher wants to know if taking music lessons will help improve IQ. On average, from a group
of 49 participants, the IQ score from a group taking music lessons was 104.2. What is the probability of
observing this average or higher if the true average is 100?
2.) Suppose a researcher obtains a p-value of 0.0423 where the set α value is 0.05. Statistically, what
would the conclusion about the null hypothesis be?
3.) In the situation described above in section 1 e,
a.) State the null and alternative hypothesis for the experiment.
b.) With a set α = 0.05, would the researcher have found statistically significant results?
c.) In terms of practical significance, do you feel that the results of the experiment described have
practical significance? Explain.
d.) What would a type 2 error be in this experiment?
4.) Describe in your own words what “statistical power” is.
5.) An experimenter wants to test whether or not a drug is useful for reducing systolic blood pressure.
A decrease of 5mmHg is considered scientifically significant and this needs to be demonstrated at 98%
confidence. The population standard deviation of systolic bp is 14 points. How many people should this
drug be tested on (at minimum) to be able to justify this claim?