Psychology 302

Psychology 302, Winter 2020 Correlational Approaches to Research

Problem Set 4, due Wednesday, March 4th in class

1. For each of the following, determine whether the decision reached by the researcher in the first sentence is correct, given the information in the

subsequent sentences. If the decision is incorrect, indicate what type of error was made.

a. Based on an initial test, a medical researcher concluded that Serum A was not effective for treating a disease. However, 25

years later, many subsequent studies have found that Serum A is effective, and it is now used regularly to treat the disease.

b. A researcher who studied literacy concluded that children who were raised by parents who read to them regularly learned to

read earlier than children whose parents did not read to them.

This finding has been consistently demonstrated in subsequent studies over many years.

c. Researchers originally claimed that students who were homeschooled performed worse in college compared to students

with public education. However, over many years, studies have subsequently shown that home schooled children perform

equally well in college as public school students. d. A researcher found that adults who followed a low fat diet did

not lose any more weight compared to adults who were not dieting. Several years of subsequent research have shown that

low fat diets are not effective compared to not dieting.

For problems 2-4, use the logic of hypothesis testing to answer the research

question posed. Be sure to go through each of the formal steps. Clearly

state your null and alternate hypotheses, your obtained and critical statistics, and whether you can reject the null. Be sure to clearly state your

conclusions in words.

2. A researcher is testing the effectiveness of a new drug that is intended to

improve learning and memory performance. A random sample of 16 rats are given the drug and then tested on a standard learning task. The

mean of the sample is 56.5. In the general population of rats (with no drug), the average score on the standardized test is normally distributed

with a mean of  = 51.9 and a standard deviation of x = 10.2. Is there

evidence that the drug improves memory scores? Set  = .05.

3. You notice that a lot of students listen to music while studying at the library, and you suspect that this may be detrimental to their learning.

You take a random sample of Intro Psychology students who listen to music while studying and you measure their scores on the Intro Psych

final exam. In the population of ALL intro psych students, the final exam is normally distributed with a mean of  = 79.1 and a standard deviation

of  = 6.1. In your sample of 22 music-listening students, the mean

was X = 76.15. Is there evidence to conclude that listening to music is detrimental to exam performance? Set  = .05.

4. A common reading achievement test for fifth grade students has a

nationwide mean of  = 70.0. A teacher would like to know if students

who receive a new type of reading skills training are significantly different

from the national average, but she doesn’t know whether they’re likely to be better or worse than average. She trains her class of N = 31 students

with the new technique and then gives them the test. The class average

is X = 72.9 with a standard deviation of Sx= 7.5.

a. Using the formal logic of null hypothesis testing, test whether the students differ from the national average, setting  = .01.

b. Would this test be significant if you had set  = .05? Explain

why you reached a different conclusion depending on what alpha

level you used.