Chapter 9,10,11 Psych Stats
True or False, a T statistic, the estimated standard error provides a measure of howe much difference is reasonable to expect between a sample mean and the population mean
True
In an independent measure T hypothesis test, how is the T statistic related to the amount of difference between the two sample mean
the larger the difference between means, the larger the value for T (farther from zero.)
Which set of sample characteristics is most likely to produce a significant difference for an independent - measures T test
A large sample mean difference and small sample variances. The greatest difference between samples occurs with a big mean difference and small variances
A sample of n=9 scores has a mean of M=46 and a variance of S2=36. what is the estimated standard error for this sample?
2
Choen's D is computed by first finding the difference between the two sample means and the dividing by the pooled variance
False
A researcher reports a T statistic with DF= 30. the statistic was computed for a sample of n=29 scores
False a sample of n=31 would have a df=30 df=n-1 df=31-1 and df-30
If all other factors are held constant, an increase in the magnitude of M D will cause a decrease in the size of the T static
False the larger the larger the mean difference + the large the value for T
In a hypothesis test, the larger the value for the sample variance, the more likely it is that you will reject the null hypothesis
False the larger the sample variance, the less likely it is that you will reject the null hypothesis
As the variance of difference scores increases, the value of the T statistic also increases (farther from zero)
False the larger the variance the smaller the value for T
A researcher would like to compare two treatment conditions using a sample of 30 scores in each treatment. If a repeated measures design is used, the study will require a total of n= 60 participants
False the same 30 subjects will be used in both treatment conditions
For a two- tailed hypothesis test with a =.05 and a sample of n=25 scores, the boundaries for the critical region would be T= +- 2.060
False with a DF= 24 the critical values are +-2.064
If a treatment has a consistent effect, then the sample of difference scores will have a large value for variance.
False, a consistent effect will produce small variance for the difference scores.
As the value of DF increases the T distribution tends to become flatter and more spread out.
False, as DF increases, the T distribution becomes taller and more compact like a normal shaped distribution
The larger the values for the two sample variances, the greater the likelihood that the independent measures T test will find. A significant difference. (Assume all other factors are held constant.)
False, increases in variance produce a smaller value for T (nearer to zero.)
True or false, a sample of n=25 scores with a sample variance of S2 = 100 would have an estimated standard error of 4 points
False, the estimated standard error is the square root of 4.
True or False, the null hypothesis for an independent measure T- test states that the two sample means are equal
False, the null hypothesis states that the two population means are equal
In general, using a repeated measures design to evaluate the difference between two treatments will produce a larger standard error than would be obtained using an independent- measures design to compare the same two treatments
False, the repeated measure study has a smaller standard error because the variance is reduced by removing individual differences
The null hypothesis for the independent- measures T test states
There is no difference between the two population means. The null hypothesis always refers to the populations, not the samples.
For a hypothesis test with an independent measure T, the larger the difference between the two sample means, the greater the likelihood that you will reject the null hypothesis.
True
For an independent - measures T statistic, the magnitude of the estimated standard error is inversely related to the size of the samples (the bigger the samples, the smaller the error)
True
True or False: A researcher is evaluating the effectiveness of a new cholesterol medication by measuring cholesterol levels for a group of men before they take the medication and then measuring cholesterol levels for a group of men before they take the medication and then measuring again after the men have been taking the medication for 4 months. This is an example of repeated measurement studies
True
With a repeated measures design it Is possible to evaluate the difference between two treatments using only one sample of subject
True
A sample of n= 16 individuals is selected from a population with M=80 add a treatment Is administered to the sample. Mean is M= 84 and the sample variance is S2= 100. if Cohens D is used to measure effect size for this study what value will be obtained for D?
0.40
A repeated- measures study would be appropriate for which of the following situation?
A researcher would like to compare individuals from two different populations. Two different populations will require two different samples
A sample of n=4 individuals is obtained from a population with M=80. Which set of sample statistics would produce the most extreme value for it.
M= 88 and S2= 8
A sample of n= 25 scores is obtained from a population with M=80. Which of the following sets of sample statistics will produce the most extreme value for the T statistic?
M=90 with S2= 10
The two sample means are 10 and 20 with variances of 120 and 125
The greatest difference between samples occurs with a big mean difference and small variances
Homogeneity of variance assumes that the two population variances are equal.
True
If two samples each have N = 5 and SS =40 then the pooled variance is 10.
True
In a hypothesis test a T statistic near zero indicates that the sample mean is relatively close to the population mean that is specified in the null hypothesis
True
Measures of effect size (such as Cohen's D and R2.) are relatively unaffected by the size of the sample
True
One concern with a repeated measures design is that a participants performance in one treatment condition may be influenced by previous experience in another treatment condition
True
One sample has n= 8 scores and SS = 40. A second sample has N = 4 scores and SS = 20. The pooled variance for these two samples is 60/10= 6
True
True or False, to calculate a statistic you must first compute the sample mean and the same variance (or sample standard deviation)
True
True or false, The larger the value for DF the more a T distribution resembles a normal distribution
True
Two separate samples, each with n= 9 will produce an independent measures T statistic with df= 16
True
As the sample variance increases the value of the T statistic
decreases (moves toward zero)
For a repeated- measures hypothesis test, the null hypothesis states
for the individuals in the entire population there is no consistent difference between the two treatments. The null hypothesis states that there is no difference for the entire population.
A researcher reports a T statistic with df= 20. Based on this information, how many individuals were in the sample?
21
A researcher reports in independent measures T statistic with DF =20. what is the total number of subjects who participated in the research study?
22
A researcher is comparing two treatment conditions with a sample of n= 10 is one treatment and a separate sample of n= 15 in the other. If the data are evaluated with an independent- measures T statistic, whats the DF value for the statistic?
23
The estimated standard error SM, provides a measure of the average or standard discrepancy between
A sample mean and the population mean. The estimated standard error measures the standard distance between M and M.
Holding everything else constant, increasing sample size _____
All of the other options are consequences of increasing sample size. Increasing and decreases the error in the denominator of the T statics.
To calculate a T statistic, what information was needed from the sample?
All of the other options are needed to compute T. The statistic requires the sample variance as well as M and n
For an independent - measures research study, one sample has M=20 with S= 22 and age second sample has M=17 and S= 28. The pooled variance is 25. What is the estimated value of Cohens D for this data
D = 3/5
One sample of N= 10 scores has a variance of S2 = 10 and a second sample of n=10 scores has S2=20. If the pooled variance is computed for these two samples, then the value obtained will be.
Exactly half way between 10 and 20.
A sample of n= 15 scores produces a T statistic of T= -2.96. If a researcher is using a regular two tailed test with a =. 01 what decision should be made?
Fail to reject the null hypothesis
A researcher reports an independent measures to statistics with DF= 20. based on the DF value, you can conclude that the study used a total of 21 participants
False
Which of the following sets of data would produce the largest value for an independent measures T statistic
The two sample means are 10 and 20 with variances of 20 and 25
With a= .05 the two tailed critical region for a sample n=10 participants would have boundaries of ____
T= +-2.262
A sample of n=25 scores has a mean of M=40v and a variance of S2=100. If this sample is being used to test a null hypothesis stating that M= 43 what is the T statistic for the sample.
T= -3/2 = -1.50
In what circumstances is the T statistic is used instead of a z-score for a hypothesis test?
The T statistic is used when the population variance or standard deviation is unknown. The T statistic uses the sample variance to estimate the unknown population value.
In an Independent- measures T hypothesis test, how does the magnitude for sample variance influence the size of the T statistic
The larger the sample variance the smaller the T value (closer to zero)
The magnitude of the sample variance has no influence on the T value
The larger the variance the larger the standard error, the smaller the T value
The homogeneity of variance assumption states that ____
The sample comes from populations with equal variances. Homogeneity requires that the two populations have the same variance
What is the estimated standard error for a sample of n=9 scores with s2 =36
The square root of 36/9
As the sample size increases, what happens to the critical values for it? (assume that the alpha level and all other factors remain constant.)
The values decrease. As df increases the T distribution becomes less spread out.
a repeated- measures T statistic with a DF= 20 indicates that a total if 21 subjects participated In the research study.
True
The null hypothesis for a repeated- measures T test concerns the entire population of difference scores, not just the D values in the sample.
True, the null hypothesis always refers to the population
With a =.05, the critical values for a two- tailed z- score test are +- 1.96. The corresponding values for a two - tailed test with a= .05 tends to be ___
greater than 1.96 farther from zero. Especially when N is small, + statistics are more variable than z-scores and form a flatter, more spread distribution
One sample has n=25 scores and a second sample has n= 15 scores. If the pooled variance is computed for the two samples, then the value for the pooled variance will be.
between the two sample variances, but closer to the variance of the larger sample.
Which of the following research situations would be most likely to use an Independent measures design?
compare the mathematics skills for 9th grade boys versus 9th grade girls. Comparing boys and girls would require two separate samples.
