psych 221 exam 2
Which of the following statistics are examples of descriptive statistics?
M and SD µ and s range and variance
Which of the following accurately describes the critical region?
Outcomes with a very low probability if the null hypothesis is true
If a hypothesis test produces a z-score in the critical region, what decision should be made?
Reject the null hypothesis
What is measured by the numerator of the z-score test statistic?
The actual distance between M and µ
Which of the following is a fundamental difference between the t statistic and a z-score?
The t statistic uses the sample variance in place of the population variance.
A researcher selects a sample and administers a treatment to the individuals in the sample. If the sample is used for a hypothesis test, what does the null hypothesis (H0) say about the treatment?
The treatment has no effect on the scores.
With α = .05 and df = 8, the critical values for a two-tailed t test are t = ±2.306. Assuming all other factors are held constant, if the df value were increased to df = 20, what would happen to the critical values for t?
They would decrease (move closer to zero).
A one-sample t-test allows the researcher to determine whether the means in the experimental and control group differ.
false
If a hypothesis test leads to rejecting the null hypothesis, it means that the sample data failed to provide sufficient evidence to conclude that the treatment has an effect.
false
If two samples from the same population are the same size and have the same mean, then they will have the same t statistic.
false
In Step 3, what type of t-test is this?
independent t-test
In Step 2, what are the t values that create the critical region?
less than -1.98 and more than 1.98
A researcher conducts a hypothesis test using a sample from an unknown population. If the one-sample t statistic has df = 30, how many individuals were in the sample?
n = 31
In Step 4, what is your conclusion from the hypothesis test?
reject the null
Compared to a z-score, a hypothesis test with a t statistic requires more information from the sample.
true
The denomentor in the formula for a one-sample t-test and an independent sample t-test are calculated differently, but conceptually are the same - estimated standard error.
true
In Step 3, what is the t-statistic?
-2.5
In Step 3, what value goes in the denominator of the t test formula?
0.2
The results of an independent-samples t-test are reported as follows: t(15) = 2.70, p < .05. Based on this report, how many individuals were in the sample?
17
If an effect is true in reality, but the researcher fails to find evidence for it in their sample, what error has been made?
A Type II error
Which set of characteristics will produce the smallest value for the estimated standard error?
A large sample size and a small sample variance
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
Which of the following best describes a Type I error?
False positive
When n is small (less than 30), how does the shape of the t distribution compare to the normal distribution?
It is flatter and more spread out than the normal distribution.
If other factors are held constant, what is the effect of increasing the sample size on hypothesis testing?
It will decrease the estimated standard error and increase the likelihood of rejecting H0.
