Exam III Review Flashcards
A binomial experiment has the following properties…
A fixed number (n) of trials.
The result of each trial falls into one of two categories.
* Usually denoted “success” or “failure”
Each trial is independent.
The probability of success (p) is the same for every trial.
Binomial distributions are
Symmetric when _______.
p = 0.5
Binomial distributions are
Positively skewed when _______.
p < 0.5
Binomial distributions are
Negatively skewed when _______.
p > 0.5
Binomial standard error _______.
Increases with n
Increases as p and (1 – pi)
approach 0.5
Binomial mean _______.
increases with n and with pi
A binomial variable X is just _______.
the sum of n independent and
identical Bernoulli variables Y
T or F
The sampling distribution of the proportion is not a binomial distribution.
T, It’s a scaled down version
In which of the following cases will the binomial distribution be perfectly symmetric?
A. pi = 0.1 and n = 100
B. pi = 0.95 and n = 100
C. pi = 0.95 and n = 20
D. pi = 0.1 and n = 20
E. pi = 0.5 and n = 20
E. pi = 0.5 and n = 20
T or F
In poll for an election involving two candidates, the margin of error for the difference between the candidates’ proportions is the same as the margin of error for the leading candidate.
F
Which of the following statements about the margin of error is TRUE?
T or F
In a political poll, the reported margin of error typically corresponds to the 95% confidence interval.
T
Which of the following statements about the margin of error is TRUE?
T or F
For a given sample size, the margin of error for a single proportion is smaller when the observed proportion is 0.5 than when it is 0.8.
F
Which of the following statements about the margin of error is TRUE?
T or F
To reduce the margin of error for one proportion by a factor of 2, you need to double the sample size.
F
Imagine that you are comparing the means from two samples, and that one of the samples is larger than the other. Which of the following statements about an equal-variance two-sample t test is FALSE?
T or F
The degrees of freedom for the test equal the sum of the two sample sizes minus 2.
T
Imagine that you are comparing the means from two samples, and that one of the samples is larger than the other. Which of the following statements about an equal-variance two-sample t test is FALSE?
T or F
In the calculation of the pooled variance, the larger sample gets more weight than the smaller sample.
Correct!
T
Imagine that you are comparing the means from two samples, and that one of the samples is larger than the other. Which of the following statements about an equal-variance two-sample t test is FALSE?
T or F
For a two-tailed test with alpha = .05, the critical value of t is +/– 1.960.
F
Imagine that you are comparing the means from two samples, and that one of the samples is larger than the other. Which of the following statements about an equal-variance two-sample t test is FALSE?
T or F
If the p-value for a two-tailed test is less than .05, the 95% confidence interval for the difference between the means will NOT include zero.
T
Holding the sample size constant, at what value of pi (the population proportion) will the standard deviation of the sampling distribution of the proportion be largest?
A. 0.25
B. 1
C. 0.5
D. 0
E. The standard deviation does not depend on pi.
C. 0.5
Which of the following statements about Cohen’s d is FALSE?
It is an effect size measure for the difference between the means of two samples.
Because n is in the denominator, Cohen’s d is very sensitive to sample size.
It has the same sign as the calculated t statistic.
It is equal to the difference between two means, divided by the pooled standard deviation.
Because n is in the denominator, Cohen’s d is very sensitive to sample size.
A choice experiment has 2 conditions (A and B) and three choice options (1, 2, and 3). There are 150 participants, 72 in condition A and 78 in condition B. Across both conditions, 88 participants choose option 1, 46 participants choose option 2, and 16 participants choose option 3. For a chi-square test of independence, what it the expected number of participants in condition A that choose option 3?
7.68
25.00
24.00
8.00
7.68
In a two-tailed test of whether two proportions from independent samples are equal, the p-value is .15. What is the correct interpretation of this p-value?
Assuming the null hypothesis that the two proportions are equal is true, the chance of observing a difference as extreme as or more extreme than the one observed, in the same direction, is .15.
Assuming the null hypothesis that the two proportions are equal is true, the chance of observing a difference as extreme as or more extreme than the one observed, in either direction, is .15.
Based on the observed difference between the proportions, there is a .15 chance that the alternative hypothesis that the proportions are different is true.
Based on the observed difference between the proportions, there is a .15 chance that the null hypothesis that the two proportions are equal is true.
Assuming the null hypothesis that the two proportions are equal is true, the chance of observing a difference as extreme as or more extreme than the one observed, in either direction, is .15.
