Question

1. Alpha is the probability of committing a Type I Error if…

a. The null distribution is true

b. The null distribution is false

c. n is larger than 30

d. the alternative distribution is true

2. We are more likely to reject the null as…

a. Alpha goes down

b. n goes down

c. variation goes down

d. the difference between sample and population mean goes down

3. Which of the following is true of a one-tailed test?

a. It’s more difficult to reject the null than with a two-tailed test

b. It’s more flexible than a two-tailed test

c. It’s more sensitive than a two-tailed test

d. It’s more appropriate when there are competing theories than a two-tailed test

4. Which of the following is not a component of Cohen’s D?

a. Sample Mean

b. Population/Hypothesized Mean

c. Standard deviation

d. Sample Size

5. When we reject the null hypothesis, we are saying that…

- we have proven the alternative hypothesis to be true
- we have proven the null hypothesis to be false
- our sample is too unlikely to have been produced by the null distribution
- our sample had a mean approximately the same as the population
- our sample had a standard deviation smaller than the population

6. If our α = .05, we should make Type I Errors ___% of the time?

- 2.5
- 5
- 95
- .01
- .025

7. The population of adults with tablets and/or smartphones get an average of 6 hours

(µ = 6 and σ = 2) of sleep a night. To see whether electronic use was interfering with sleep, researchers had a sample of 25 adults turn off their smartphones and tablets 1 hour before going to bed. This sample got an average of 6.9 hours of sleep a night. Assuming the population is normally distributed, use an alpha of .05 to test the hypothesis that turning off their electronics early increased the number of hours of sleep they got.

a. Specify the null and alternative hypotheses.

b. Report the critical value, the SE, and the test statistic

c. Report your decision in a sentence

d. What type of error did you risk making?

8. A company uses a productivity measure to assess how efficiently employees use their time at work. The population of employees had an average productivity rating of 55 (µ=55 and σ = 21). To see how working from home (sometimes called telecommuting) would affect productivity the company selected a sample of 49 employees to work from home. Their average productivity rating was 48. Test the hypothesis that working from home affected productivity using an alpha of .01.

a. Specify the null and alternative hypotheses.

b. Report the critical value, the SE, and the test statistic

c. Report your decision in a sentence

d. What type of error did you risk making?

9. Psychologists have found that in the population, people can store about 7 pieces of informztion in their short-term memory (µ = 7, σ = 1), normally distributed. Researchers developing a mnemonic device to increase short-term memory used a sample of 9 people to test their device. The average memory from the sample was 8 pieces of information.

Test the hypothesis that the mnemonic device improved short-term memory using alpha = .01

a. Specify the null and alternative hypotheses.

b. Report the critical value, the SE, and the test statistic

c. Report your decision in a sentence

d. Calculate Cohen’s D for the effect size. Does it appear small, medium or large?

Answer #1

1) alpha is the probability of rejecting null hypothesis when null hypothesis is true

Option a is correct

2) alpha goes down is more likely to reject the null hypothesis

option a is correct

3) In one tiled test, then the rejection of the null hypothesis is more difficult. but two tailed test they have two portions of the rejection region the the rejection of the null hypothesis is more easily.

Option a is correct

4) The compnent of Cohen's D statistics are sample mean, standard deviation and sample size

the population/ hypothesized mean is not a component of d statistics

Option b is correct

PSYC 220: Homework 4
Note: In the case of decimals, round to the nearest hundredths
place (ex: 9.37)
1. Alpha is the probability of committing a Type I Error if…
a. The null distribution is true
b. The null distribution is false
c. n is larger than 30
d. the alternative distribution is true
2. We are more likely to reject the null as…
a. Alpha goes down
b. n goes down
c. variation goes down
d. the difference between...

The population of adults with tablets and/or smartphones get an
average of 6 hours (µ = 6 and σ = 2) of sleep a night. To see
whether electronic use was interfering with sleep, researchers had
a sample of 25 adults turn off their smartphones and tablets 1 hour
before going to bed. This sample got an average of 6.9 hours of
sleep a night. Assuming the population is normally distributed, use
an alpha of .05 to test the hypothesis...

1. Type 1 error is:
a. the probability of rejecting the alternative hypothesis even
though it is true.
b. the probability of accepting the alternative hypothesis even
though it is false.
c. the probability of rejecting the null hypothesis even though
it is true.
d. the probability of accepting the null hypothesis even though
it is false.
2.
Conclusions about population parameters made from confidence
intervals (CI) and hypothesis tests (HT) are the same when they use
the same a...

The probability of committing a Type I error when the null
hypothesis is true as an equality is
a. The confidence level
b. p
c. Greater than 1
d. The level of significance

Some researchers claim that herbal supplements improve human
memory. To test this claim, a researcher selects a sample of n = 25
college students. Each student is given herbal supplements daily
for 6 weeks and then all the participants are given a standardized
memory test. For the population, scores on the tests are normally
distributed with µ = 70 and σ= 15. The sample of n = 25 students
had a mean score of M = 75. Can we conclude...

Multiple Choice Questions
Q1. In a hypothesis test, Beta is best described
by
P (Type I error)
P (Test Stat>|Observed Stat|)
Power
P (Type II error)
Q2. Which alternative hypothesis would I need
to double the p-value in a test for the mean?
No feasible answer
Lower tailed alternative
Two sided alternative
Upper tailed alternative
Suppose our p-value is .184. What will our conclusion be
at alpha levels of .10, .05, and .01?
We will reject Ho at alpha=.10 or...

(1 point)
Type I error is:
A. Deciding the null hypothesis is true when it is
false
B. Deciding the alternative hypothesis is true
when it is false
C. Deciding the null hypothesis is false when it
is true
D. Deciding the alternative hypothesis is true
when it is true
E. All of the above
F. None of the above
Type II error is:
A. Deciding the null hypothesis is false when
it is true
B. Deciding the alternative hypothesis...

6. Personality researchers wondered if there were differences
between "dog people" and "cat people" in how extraverted they were.
To find out if there are any differences, researchers asked people
to self-identify as cat or dog people and then complete a
personality inventory. The results of the extraversion test (on a
scale from 0-100) for the two types of person are presented
below.
"Dog People" Sample: M = 83, SS = 360, n = 10
"Cat People" Sample: M =...

1. According to a recent report, 38% of adults wait
until they are 30 years of age or older to get
married for the first time. A researcher believes this claimed
value is too low. He gathers
data in order to test the hypotheses Ho: p = 0.38 vs. Ha: p >
0.38. In these hypotheses, what
does p represent?
A. The sample proportion
B. The population proportion
C. The p-value
D. The sample mean
E. The population mean
2....

True or False
1. Hypothesis tests are robust to the significance level you
choose, meaning regardless of the alpha level: .10, .05, or .01,
our test will have the same conclusion or result.
2. If alpha is greater than the p-value, then we reject the null
hypothesis.
3. The p-value is strictly the probability the null hypothesis
being true.
4. Hypothesis tests are accessing the evidence provided by the
data and deciding between two competing hypotheses about the
population parameter....

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