STAT 200 Quiz 3

STAT 200 Quiz
3

1.
A researcher
believed that there was a difference in the amount of time boys and girls at 7th grade studied by using a two-tailed t test. Which of the
following is the null hypothesis?

a.Mean of hours that boys studied per day was equal to mean
of hours that girls studied per day
b.Mean of hours that boys studied per day was greater
than mean of hours that girls studied per day
c.Mean of hours that boys studied per day was smaller
than mean of hours that girls studied per day
d.Mean of hours that boys studied per day was smaller
than or equal to mean of hours that girls studied per day

2.
A professor assumed
there was a correlation between the amount of hours people were expose to
sunlight and their blood vitamin D level. The null hypothesis was that the
population correlation was__

a.Positive 1.0
b.Negative 1.0
c.Zero
d.Positive 0.50

3.
Conventionally, the
null hypothesis is false if the probability value is:

a.Greater than 0.05
b.Less than 0.05
c.Greater than 0.95
d.Less than 0.95

4.
A teacher
hypothesized that in her class, grades of girls on a chemistry test were the
same as grades of boys. If the probability value of her null hypothesis was
0.56, it suggested:

a.We failed to reject the null hypothesis
b.Boys’ grades were higher than girls’ grades
c.Girls’ grades were higher than boys’ grades
d.The null hypothesis was rejected

5.
Which of the following could reduce the rate of Type I error?

a. Making the significant level from 0.01 to 0.05
b. Making the significant level from 0.05 to 0.01
c. Increase
the ? level
d. Increase the power

6.
___is the
probability of aType II error; and
___ is the probability of correctly rejecting a false null hypothesis.

a.1-?; ?
b.?; 1-?
c.?; ?
d.?; ?

7.
A student hypothesized that girls in his class had the same blood pressure
levels as boys. The probability value for his null hypothesis was 0.15. So he
concluded that the blood pressures of the girls were higher than boys’. Which
kind of mistake did he make?

a. Type I
error
b. Type II error
c. Type I and Type II error
d. He did not make any mistake

8.
When you conduct a hypothesis testing, at which of the following P-value, you
feel more confident to reject the null hypothesis?

a. 0.05
b. 0.01
c. 0.95
d. 0.03

9.
A student posed a
null hypothesis that during the month of September, the mean daily temperature
of Boston was the same as the mean daily temperature of New York. His
alternative hypothesis was that mean temperatures in these two cities were
different. He found the P value of his null hypothesis was 0.56. Thus, he could
conclude:

a.In September, Boston was colder than New York
b.In September, Boston was warmer than New York
c.He may reject the null hypothesis
d.He failed to reject the null hypothesis

10.
If the P-value of a
hypothesis test is 0.40, you conclude

a.You accept the null hypothesis
b.You reject the null hypothesis
c.You failed to reject the null hypothesis
d.You think there is a significant difference

11.
A teacher assumed that the average of grades for a math test was 80. Imagine 20
students took the test and the 95% confidence interval of grades was (83, 90).
Can you reject the teacher’s assumption?

a. Yes
b. No
c. We cannot tell from the given information

12.
Which of the following descriptions of confidence interval is correct? (Select
all that apply)

a. If a 99% confidence interval contains 0, then
the 95% confidence interval contains 0
b. If a 95% confidence interval contains 0, then
the 99% confidence interval contains 0
c. If a 99% confidence interval contains 1, then
the 95% confidence interval contains 1
d. If a 95% confidence interval contains 1, then
the 99% confidence interval contains 1

13.
If a statistical test result is not significant at the 0.05 level, then we can
conclude:

a. It is not significant at 0.01 level
b. It is not significant at 0.10 level
c. It must be significant at 0.01 level
d. It must
be significant above 0.05 level

14.
Power is equal to:

a. ?
b. ?
c. 1-?
d. 1-?

15.
Which of the
following descriptions of null hypothesis are correct? (Select all that apply)

a.A null hypothesis is a hypothesis tested in significance
testing.
b.The parameter of a null hypothesis is commonly 0.
c.The aim of all research is to prove the null
hypothesis is true
d.Researchers can reject the null hypothesis if the
P-value is above 0.05

16.
Imagine that a researcher wanted to know the average weight of 5th grade boys in a high school. He randomly
sampled 5 boys from that high school. Their weights were: 120 lbs., 99 lbs, 101
lbs, 87 lbs, 140 lbs. What’s the samplestandard
deviation?
Mean
weight,.0/msohtmlclip1/01/clip_image002.png”>
Then,
the sample standard deviation,
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17.
Imagine that a researcher wanted to know the average weight of 5th grade boys in a high school. He randomly
sampled 5 boys from that high school. Their weights were: 120 lbs., 99 lbs, 101
lbs, 87 lbs, 140 lbs. What’s thestandard
error of the mean?
The
standard error of the mean,.0/msohtmlclip1/01/clip_image006.png”>

18.
Imagine that a researcher wanted to know the average weight of 5th grade boys in a high school. He randomly
sampled 5 boys from that high school. Their weights were: 120 lbs., 99 lbs, 101
lbs, 87 lbs, 140 lbs. The researcher posed a null hypothesis that the average
weight for boys in that high school should be 100 lbs. What is theabsolute value of calculated t
that we use for testing the null hypothesis?

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The test statistic,.0/msohtmlclip1/01/clip_image010.png”>

19.
Imagine a
researcher posed a null hypothesis that in a certain community, the average
energy expenditure should be 2,100 calories per day. He randomly sampled 100
people in that community. After he computed the t value by calculating a
two-tailed t-statistic, he found that the probability value was 0.10. Thus, he
concluded:

a.The average energy expenditure was bigger than
2,100 calories per day
b.The average energy expenditure was smaller than
2,100 calories per day
c.He could not reject the null hypothesis that the average
energy expenditure was 2,100 calories per day
d.The average energy expenditure was either more than
2,100 calories per day or less than 2,100 calories per day

20.
Compared to the
normal distribution, the t distribution has ___ values at the top and ___ at
the tails.

a.More; less
b.More; more
c.Less; less
d.Less; more

21.
In order to test if
there is a difference between means from two populations, which of following
assumptions areNOT required?

a.The dependent variable scores must be a continuous
quantitative variable.
b.The scores in the populations are normally
distributed.
c.Each value is sampled independently from each other
value.
d.The two populations have similar means

22.
A researcher posed a null hypothesis that there was no significant difference
between boys and girls on a standard memory test. He randomly sampled 100 girls
and 120 boys in a community and gave them the standard memory test. The mean
score for girls was 70 and the standard deviation of mean was 5.0. The mean
score for boys was 65 and the standard deviation of mean was 6.0. What’s the
absolute value of the difference between means?

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Now, the absolute value of the difference between means,.0/msohtmlclip1/01/clip_image014.png”>

23.
A researcher posed a null hypothesis that there was no significant difference
between boys and girls on a standard memory test. He randomly sampled 100 girls
and 100 boys in a community and gave them the standard memory test. The mean
score for girls was 70 and the standard deviation of mean was 5.0. The mean
score for boys was 65 and the standard deviation of mean was 5.0. What is the
standard error of the difference in means?

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24.
A researcher posed a null hypothesis that there was no significant difference
between boys and girls on a standard memory test. He randomly sampled 100 girls
and 100 boys in a community and gave them the standard memory test. The mean
score for girls was 70 and the standard deviation of mean was 5.0. The mean
score for boys was 65 and the standard deviation of mean was 5.0. What’s the
t-value (two-tailed) for the null hypothesis that boys and girls have the same
test scores?

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25.
Which of the following involves making pairwise comparisons?

a. Comparing the standard deviation of GRE grades
between two states
b. Comparing the variance of the amount of soda
consumed by boys and girls in a high school
c. Comparing
the mean weight between children in grades 2, 3, 4 and 5
d. Comparing the number of restaurants in New York
and Boston

26.
A professor wanted
to test all possible pairwise comparisons among six means. How many comparisons
did he need to compare?

a.5
b.6
c.10
d.15

27.
A professor wants to test all possible pairwise comparisons among three means.
If we need to maintain an experiment –wise alpha of 0.05, what is the error
rate per comparison after applying Bonferroni correction?

# of comparisons = 3C2 = 3 Error rate per
comparison = 0.05/3 = 0.0167

28.
Which of the
followings can increase the value of t? (select all the apply)

a.Increase the standard deviation of difference
scores
b.Decrease the standard deviation of difference
scores
c.Increase the difference between means
d.Decrease the difference between means

29.
Imagine a researcher wanted to test the effect of the new drug on reducing
blood pressure. In this study, there were 50 participants. The researcher measured
the participants’ blood pressure before and after the drug intake. If we want
to compare the mean blood pressure from the two time periods with a two-tailed
t test, how many degrees of freedom are there?

a. 49
b. 50
c. 99
d. 100

30.
Which of the followings is the definition of power?

a. Power is the probability of rejecting a null
hypothesis
b. Power is the probability of accepting a null
hypothesis
c. Power is the probability of accepting a false
null hypothesis
d. Power is
the probability of rejecting a false null hypothesis

31.
The probability of failing to reject a
false null hypothesis is ____

a.
?

b.
1-?

c.
1-?

d. ?

32.
If power is big, you can assume:

a. The difference between the means is more likely
to be detected
b. The
significance level set by the researcher must be high
c. We increase the probability of type I error
d. Your study result will be more likely to be
inconclusive

33.
If the probability that you will correctly reject a false null hypothesis is
0.80 at 0.05 significance level. Therefore, ? is__ and ? is__.

a. 0.05, 0.20
b. 0.05, 0.80
c. 0.95, 0.20
d. 0.95, 0.80

34.
As the sample size increases, we assume:

a. ? increases
b. ?
increases
c. The probability of rejecting a hypothesis
increases
d. Power increases

35.
Which of the following can increase power?

a. Increasing standard deviation
b.
Decreasing standard deviation
c. Increasing both means but keeping the difference
between the means constant
d. Increasing both means but making the difference
between the means smaller