Psych Stats Final
for the following frequency distribution what is the proportion associated w x=3
.10
For any distribution, what is the z-score corresponding to the mean?
0
On average what value expected for the t-statistic when the null hypothesis is true?
0
what portions of a normal distribution is located in the tail beyond z=2.00
0.0228
a vertical line is drawn through a normal distribution at z= 0.80. what proportion of the distribution is on the right- hand side of the line?
0.2119
John drives to work every morning and trip takes an average of μ=38 mins. The distribution of driving times approx normal with standard deviation of σ= 5 minutes. for a randomly selected morning, what is the probability that johns work will take less than 35 minutes?
0.2743
on an exam with population mean of 70, you have a score of 75 which of the following values for the standard deviation would give you the highest position in class?
1
For an experiment comparing two treatment conditions, an independent measures design would obtain __ scores for each subject and repeated measures design would obtain _ scores for each subject
1,2
on average what value is expected for the F-ratio if the null hypothesis is true
1.00
an independent measures study comparing two treatment conditions produces a t-stat with df=18. if the two samples are the same size. how many participants were in each of the samples?
10
correlational study
2 variables are measured and there is only 1 group of participants
an anyalsis of variance produces SS(total)= 40 and SS (within)=10, what is SS (between)?
30
sample of size n=4 are selected from a population of μ= 80 σ=8 what is the standard error for the distribution of sample means?
4
for a perfectly symmetrical distribution with a mean of 40 what is the value of the median?
40
the following data obtained from a repeated measures research study what is the value of SS for the difference of scores?
6
The data from an independent-measures research study produce a sample mean difference of 6 points an estimated standard error of 2 points. If there are n = 8 scores in each sample, then what is the value for the t-statistic?
6/2
One sample has n = 4 scores and M = 10. A second sample has n = 6 scores and M = 5. If the two samples are combined, then what is the mean for the combined sample?
7
for a population with μ=100 and σ=20, what is the x-value corresponding to z=-0.75
85
which of the following accurately describes the an independent measure study?
It uses different groups of participants for each of the treatments being compared
which of the following samples will produce largest value for t-stat?
MD=10 SS=20
which combination of factors will produce the smallest value for standard error?
a large sample and small standard deviation
which set of characteristics will produce the smallest value for estimated standard error?
a large sample size and small sample variance
for the past 20 years, the high temperature on April 15th was average μ=62 degrees with standard deviation of σ=12. last year the high temp was 68. based on this information which of the following best describes last years temperature on April 15th?
a little above average
If a repeated-measures study shows a significant difference between two treatments with α = .01, then you can be sure that?
a significant effect does not necessarily mean that the effect size will be large.
for an independent measures, ANOVA, comparing three treatments with sample n=5 in each treatment what is critical value for the F-ratio using alpha=.05
a. 3.88
which of the following are requirements of random sample?
all other 3 choices are correct
which of the following accurately describes a hypothesis test?
an inferential technique that uses data from a sample to draw inferences about a population
what combination of factors will produce a large value for n2
b. large mean differences and small sample variance
One item on a questionnaire asks, "How many siblings (brothers and sisters) did you have when you were a child?" A researcher computes the mean, the median, and the mode for a set of n = 50 responses to this question. Which of the following statements accurately describes the measures of central tendency?
because the scores are all whole numbers, the mode will be a whole number
Last week Tom had exams in Statistics and in English. He scored 10 points above the mean on both exams. From this information, what can you can conclude about the z-scores for Tom's two scores?
both of toms z-scores are positive
for any distribution what is the z-score corresponding to the median?
cannot be determined with the given information
for which of the following situations would be related measures research design be appropriate?
comparing pain tolerance with and without acupuncture needles
for an experiment comparing more than 2 treatment conditions why should you use analysis of variance rather than separate t-tests?
conducting several t-tests would inflate risk of type I error
if an analysis of variance is used for the following data, what would the effect of of changing the values of SS1 to 50
decrease SS(within) and increase the size of the F-ratio
Organizing a set of scores into a table or a graph would be an example of using ______.
descriptive
T/F according to the central limit theorem the expected value for a sample mean becomes smaller, approaching zero as the sample size approaches infinity
false
T/F one reason for transforming x values into z scores is that the set of z scores will form a normal shaped distribution
false
True or False, in general, the larger the value of the estimated standard error, the greater the likelihood of rejecting the null hypothesis
false
a group of quiz scores ranged from 3-10 but no student has score of x=5 if scores are put into a frequency distribution table, x=5 would not be listed in the x column
false
if the sample size is doubled the standard error will always cut in half
false
t/f for an independent measures study comparing two samples with n=8 in each sample, the t- stat would have df=15
false
true or false, for a two-tailed t-test with a=.05 and a sample of n=16 the boundaries for the critical region are t= 2.120
false
what happens to the standard error of M as sample size increases?
it decreases
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
In general, if the variance of the difference scores increases, then what will happen to the value of the t statistic?
it will decrease (move toward the center of distribution)
If other factors are held constant, what is the effect of increasing the sample size?
it will decrease the estimated standard error and increase likelihood of rejecting HO
a researcher is measuring problem- solving times for a sample of 20 children. however, one child fails to solve the problem so the researcher has an undetermined score. what is the best measure of central tendency?
median
a researcher measures eye color for a sample of 50 people. which measures of central tendency would be appopiatre to summarize the measurements?
mode
which of the following is the correct null hypothesis for repeated measures t-test?
mueD=0
The students in a psychology class seemed to think that the midterm exam was very easy. If they are correct, what is the most likely shape for the distribution of exam scores?
negatively skewed
what frequency distribution graph is appropriate for scores measured on a nominal scale?
only a bar graph
which of the following accurately describes the critical region?
outcomes with a very low probability if the null hypothesis is true
Determining a person's reaction time (in milliseconds) would involve measurement on a(n) _____ scale of measurement.
ratio
the verbal SAT score for the entire class is 530 however if you select a group of 20 freshman and compute their verbal SAT score you will probabably get 530. what stastical concept is used to explain natural difference that exists between a sample mean and corresponding population mean?
sampling error
what is the final step to be performed following mathematical expression (EX)2
square the sum of all scores
in general, what is the relationship between standard deviation and and variance
standard deviation is the square root of variance
a characteristic usually a numerical value, that describes a sample is called a
statistic
with α = .05 and sample of n=15 in a repeated measures study comparing two treatments, what are the t-stats boundaries for the two-tailed critical region?
t=+- 2.145
with alpha=.01 the two-tailed critical region t-test using a sample n=16 subjects would have boundaries of
t=+- 2.947
the z-score boundaries for the critical region are determined by?
the alpha level
which of the following is a continuous variable?
the amount of time to solve a problem
what term is used to identify the mean of the distribution of sample means?
the expected value of M
The value of one score in a distribution is changed from X = 20 to X = 30. Which measure(s) of central tendency is (are) certain to be changed?
the mean
in ANOVA what is represented by the letter N?
the number of scores in the total research study
a hypothesis test with sample n=25 participants produces a t-stastic of t= +- 2.53 assuming a one-tailed test with the critical region in the right hand tail which is the correct decision?
the researcher can reject the null hypothesis with either alpha =.01 or .05
A sample of n=25 individuals is selected from a population with u=80 and a treatment is administered to the sample. What is expected if the treatment has no effect?
the sample mean should be close 80 and should lead you to fail to reject the null hypothesis
a sample has a mean of 72. if one persons score of x=58 is removed from the sample, what effect will it have on. the sample mean?
the sample mean will increase
for an independent measures research study what is measured by cohens d or r2
the size of difference between the 2 treatments
Which of the following is a fundamental difference between the T-stastic and the z-score
the t-stastitic uses sample variance in place of population variance
what is assumed by the homogeneity of variance assumption?
the two populations have equal variances
For an ANOVA comparing three treatment conditions, what is stated by the null hypothesis (Ho)?
there are no differences between any population means
the alternative hypothesis for an independent measures t-test states____?
there is a non-zero mean difference between the two populations being compared
T/F a sample mean with a z score value greater than z=3.00 would be considered extreme, unrepresentative sample
true
T/F the goal for an experiment is to demonstrate that changes in one variable are responsible for changes in a second variable
true
T/F the unit normal table can be used for any normal distribution, no matter what the values are for the mean and standard deviation.
true
T/F: A positive z-score always corresponds to an x value greater than the mean.
true
T/F: If other factors are held constant, the larger the difference between the two sample means is, the larger the value for the independent measures t-stat will be.
true
T/F: If samples are selected from a normal population, the distribution of sample means will also be normal.
true
a correlational study is used to examine a relationship between two variables but cant determine whether it is a cause and effect relationship
true
one set of scores has been placed in a grouped frequency distribution table it is impossible to determine the exact values of original scores
true
rejecting the null hypothesis with a=.01 means that you have more confidence in your decision than if you had rejected the null hyp at a=.05
true
studnets introductory art class are classified as art majors and non art majors. this is an example of a measurement on a nominal scale
true
t/f in a research report the term statically significant is used to indicate that the null hypothesis was rejected
true
t/f the researcher obtained M=27 for a sample of n=36 scores selected from a population with u=30 and σ=18. this sample mean corresponds to z-score of -1.00
true
a population distribution has σ=6. what position in this distribution is idenitifed by a z score of +2
twelve points above the mean
under what circumstances would a score of 15 points above the mean be considered an extreme score?
when the population standard deviation is much smaller than 15
under what circumstances are post hoc tests necessary?
when you reject the null hypothesis with more than 2 treatment conditions.
a normal distritubiton has a mean of μ= 24 with σ=3. what is the minimum score needed to be in the top 14% of the distribution?
x=27.24
which of the following z-scores values represent the location closest to the mean?
z=+0.50
What z-score value separates the top 10% of a normal distribution from the bottom 90%?
z=1.28
a very bright student, IQ that is three standard deviations above the mean. if the students IQ is reported as a z-score what would it be?
z=μ+3σ
which of the following symbols identifies the population standard deviation
σ
when a population with μ= 85 and σ= 12 is transformed into z-scores. after the transformation what is the standard deviation for the population of z-scores?
σ=1.00
what symbol is used to identify the standard error of m?
σM