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Multiple choice questions from Exam 2
If an entire population with M=100 and SD=20 is transferred into z-scores, then the distribution of z-scores will have a mean of …. and a standard deviation of …
0 and 1
A sample of n=9 scores has SS=200. What is the variance for this sample?
25
What term is used to refer to the mean of the distribution of sample means?
the expected value of M
What term is used to refer to the standard deviation of the distribution of sample means?
the standard error of M
On average, what value is expected (most likely) for the t statistic when the null hypothesis is true?
0
What is measured by the estimated standard error Sm?
the average difference between a sample mean and the population mean
A sample of n=25 scores is selected from a population with M=100 with SD=20. On average, how much error would be expected between the sample mean and the population mean?
4 points
What happens to the standard error of M as sample size increases?
It decreases
Which combination of factors will produce the smallest value for the standard error?
A large sample and a small standard deviation.
A sample of n=9 scores is obtained from a population with M=70 and SD=18. If the sample mean is M=76, then what os the z-score for the sample mean in the distribution of sample means?
z=1.00
A random sample of n=4 scores is obtained from a normal population with M=20 and SD=4. What is the probability that the sample mean will be greater than M=22?
0.1587
A random sample of n=16 scores is obtained from a normal population with M=40 and SD=8. what is the probability that the sample mean will be within two points of the population mean?
0.6826
A sample is obtained from a population with M=100 and SD=20. Which of the following samples would produce the most extreme (largest) z-score for the sample mean?
a sample of n=100 scores with M=104
Which of the following accurately describes a hypothesis test?
An inferential technique that uses the data from a sample to draw inferences about a population.
What is a Type I error?
concluding that a treatment has an effect when it really has no effect.
What is a Type II error?
concluding that a treatment has no effect when it really does.
Which alpha level provides the greatest risk for committing a Type I error?
.10
A researcher reports t(21)=5.30, p>0.01 for a related-samples (repeated measures) t-test. How many individuals participated in the entire experiment?
22
As sample size, n, increases
the value of df also increases, the t distribution becomes more like a normal distribution, the critical values of t get smaller
A sample size of n=4 scores has SS=48. What is the estimated standard error for the sample mean?
2
Which set of sample characteristic is most likely to result in the rejection of the null hypothesis?
A large sample size and a small sample variance
Which combination of factors produces the smallest risk of a Type II error?
alpha level .05, a large sample size and a small sample variance.
With alpha level=.05, what are the critical t values for a two-tailed single sample t-test with n=25?
t±2.064
A sample of n=25 scores produces a t statistic of t=-2.062. If the research is using a two-tailed test,
The researcher must fail to reject (retain) the null hypothesis with both alpha level .05 and alpha level .01
A sample is selected from a population with mean=60 and a treatment is administered to the sample. After treatment, the sample mean is M=66 with a sample variance of s²=100. Based on this information, the side of treatment effect, as measured by Cohens d is?
0.60
In a single sample t-test, what must be true if t=0?
The statistical conclusion is to fail to reject (retain) the null hypothesis.
Which of the following accurately describes a design that would use an independent samples t-test?
There are two groups of participants for the two treatment conditions being compared.
Which of the following is the correct null hypothesis got an independent samples t-test?
H0: u1-u2=0
An independent-measures study comparing two treatment conditions produces a t-statistic with df=18. If the two samples (groups) are the same size, how many participants were in each of the groups?
10
For an independent samples t-test, one sample has n=8 and SS=21 and a second sample has n=8 and SS=35. What is the pooled variance for the two samples?
56/14
The data from an independent-measures research study produce a sample mean difference of 4 points and a pooled variance of 16. If there are n=8 scores in each sample, then what is the estimated standard error for the sample mean difference?
2
In hypothesis testing, what is measured by Cohen’s d or r²?
The size of the effect
Note 
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