Review
A single, specific statistic that is used to test the hypotheses. Calculated from the sample data. A general term.
Test statistic
For an independent-measures study comparing two treatments with df = 48, what is n for each treatment (assuming equal number of participants in each treatment)?
n = 25 in each group
df = (n - 1)+(n-1)
? = X2 - X1
"Difference" Score (D)
The average number of traffic tickets among men and women is measured to see if there is a statistically significant difference.
Independent-samples t-test
For a repeated-measures study comparing two treatments with n = 45 scores in each treatment, what is df?
df = 44 (n-1)
The region of the distribution that consists of outcomes that are very unlikely to occur if the null hypothesis is true.
The critical region (“no H0 zone”)
A researcher obtains an independent-measures t statistic of t = 2.12 for a study comparing two treatments with a sample of n1 = 14 in one treatment and n2 = 10 in the other treatment. What is the correct decision for a regular one-tailed hypothesis test at alpha .01?
Fail to reject the null.
tcritical value = 2.508
What is another name for a repeated-measures design?
Within-subjects design
A researcher measures whether coffee intake affects hunger by recording the number of calories eaten by a sample of people in one month, then having the same group of people drink coffee for a month and record the number of calories eaten.
Dependent / related samples t-test
A researcher finds a large significant difference between women and men in leadership ability in their sample, but the reality is that there is no difference in the population. What is this an example of?
Type I error
Establishes a criterion, or "cut-off", for making a decision about the null hypothesis. Determines the risk of a Type I error.
alpha
One sample from an independent-measures study has n = 4 with SS= 100. The other sample has n= 8 and SS = 140. What is the pooled variance?
24
(SS1+SS2)/(df1+df2)
If s2 = 20 and n = 5, what is the estimated standard error?
sMD = 2
sMD = sqrt(s^2/n)
Measuring whether age has an effect on the amount of time an individual can hold his breath under water. A sample of 10-year-olds is compared with a sample of 18-year-olds.
Independent-samples t-test
One problem with these types of DESIGNS is that the participants in one group may be noticeably different (smarter, older, etc.) than those in another group and these differences may explain why the groups have different means.
independent-measures study design
z-score if X = 5, σ = 2, and µ = 6
-0.5
For an independent-measures research study, the two sample means are found to be M1 = 15.5 and M2 = 17. If the pooled standard deviation is 1.25, what would be the reported value of Cohen's d?
d = 1.2
For a repeated-measures study comparing two treatments with n = 26 scores in each treatment, the data produce t = 2.13. If the researcher is running a two-tailed test, what is the correct decision for a hypothesis test with α = .05?
Reject the null
The effect of a new exercise program is tested by measuring all the participants resting heart rate before, after, and 6 months after the program.
Repeated-measures ANOVA
An experimental study in which the researcher applies a different treatments to four different groups of individuals would use which test to detect differences between the treatments?
The (basic) standard error if σ = 100 and n = 25
An independent-measures study with n = 8 in each treatment produces M = 86 for the first treatment and M = 82 for the second treatment. The estimated standard error is 8. What is t?
t = 0.50
A repeated-measures study with 9 scores in each treatment produces a mean difference of MD= 4.0 and s = 6. If the effect size is described using Cohen’s d, then what is the value for d?
0.667
The effect of different types of note-taking on recall is tested by randomly assigning some people to take notes using laptops, some participants to take notes using a pen/paper, and some participants to take no notes.
One-way ANOVA
If cohen's d = .25, how would you describe that effect?
There was a small effect / a small difference between groups