CSBS320 Ch 7, 8, 9 (Williams EWU)
For the standard normal curve, z = _____ corresponds to a score that has 67 percent of the total area to its left. (Answer using 2 decimal places.)
0.44
If we obtain a z score of 2.5, what is our raw score for a given population mean of 800 and a standard deviation of 100? 1000 1600 900 1050
1050
Use the standard normal table (use the table reader, the table in the textbook, or a graphing calculator) to complete the statement: _____ percent of the total area under the curve is to the right of z = 0.94. (Answer using 2 decimal places.)
17.36
A university wants to select individuals for their Honors Program partly on the basis of SAT scores. Total scores for the three parts of the test are approximately μ = 1500, s = 250. If they want only the top 5 percent to qualify, what total SAT score must they equal or exceed? (Remember, SAT scores are multiples of 10.) 1910 1920 1800 1911.25
1920
What would be the cutoffs for a two-tailed t test with a p level of 0.05 and df = 3? 4.77 2.92 3.18 1.94
3.18
Suppose we create 100 different 95% confidence intervals based on 100 different samples from a population. Assuming we followed proper procedures, approximately how many confidence intervals would NOT contain the population mean? 5 95 0 50
5
The label on a can of a particular brand of extra-large olives states that there are about 33 olives in each can. A gourmet cook feels that the claim of 33 olives per can is too high and that the average number of olives per can is fewer than 33. He samples 35 cans and finds M = 32.9. What research hypothesis does he want to test? H0: μ = 33 H1: μ = 33 H1: μ < 33 H0: μ < 33
H1: μ < 33
A z score has a known mean and standard deviation. What are they? Mean=50, SD=2.0 Mean=0, SD=3 Mean=5-, SD=1 Mean=0, SD=1
Mean = 0 SD = 1
The formula for the degrees of freedom for the single-sample t test is _____. N dfX + dfY N - 1 (N - 1)(N - 1)
N - 1
The formula for the degrees of freedom for the paired-samples t test is _____. dfX + dfY N - 1 (N - 1)(N - 1) N
N-1??? {NOTdfX+dfY}
What is the difference between the denominator of the equation for the z score and that for the z statistic?
When computing a z score, you divide by the population standard deviation, but when computing a z statistic, you divide by the standard error of the sampling distribution.
Significance level (α)
reported as p .05 or .01
It is hypothesized that there is a significant difference in depression levels between men and women in a college dormitory. This hypothesis best illustrates:
research hypothesis
The formula for degrees of freedom for a single sample t test is:
df = N-1
t distribution
distribution of means when the parameters are unknown comparing 2 samples flatter than z distributions inferential statistics
A(n) _____ indicates how much the two populations do not overlap.
effect size
We calculate our statistical power and find that it is 0.93. This means that, if the null hypothesis is _____, we have a _____ chance of rejecting the null hypothesis. true; 93% false; 7% false; 93% true; 7%
false; 93%
single-sammple t test
hypothesis test comparing a sample from which we collect data to a population we know the mean but not the standard deviation 1 sample with known mean
statistical power
measure of the likelihood that we will reject the null hypothesis given that the null hypothesis is false ^ imaginary distribution = less overlap = ^ power avoiding type II error
H(0)
null hypothesis
Small _____ give evidence for the alternate hypothesis.
p values (AKA z values)
_____ are inferential statistical analyses based on a set of assumptions about the population. standardized tests non-standardized tests parametric tests nonparametric tests
parametric tests
Type I error
power (p) doesn't overlap with actual distribution imaginary distribution part
A _____ is a type of test in which we compare data from one sample to a population for which we know the mean but not the standard deviation.
single-sample t test
The difference in the calculation of standard error for the z and t statistics results in the t statistic being _____ than the z statistic. more accurate larger smaller more reliable
smaller
Robust
specific hypothesis test that produces fairly accurate results even when the data suggests that the population might not meet some of the assumptions
critical value
test statistic value beyond which we reject the null hypothesis "cutoff"
critical region
the area in the tails of the comparison distribution in which the null hypothesis can be rejected
When calculating a confidence interval for the z statistic:
the sample mean falls in the middle of the interval.
The null hypothesis states that:
the sample you are studying is not different from the population from which it was drawn.
Other things being equal, which of the following scenarios would result in the GREATEST power? N = 100; alpha = 10%; two-tailed test N = 1000; alpha 5%; one-tailed test N = 1000; alpha 10%; one-tailed test N = 1000; alpha = 5%; two-tailed test
{NOTB}
A calculated effect size of -0.75 would tell us that: our sample means were 0.75 standard deviations below the mean. the effect was small. the sample means difference and population means difference are 0.75 standard deviations apart. our sample means were 0.75 points apart.
{NOTa}
As the size of the effect of the independent variable increases, power tends to _____. increase stay the same increase or decrease depending on the number of levels of the independent variable decrease
{NOTdecrease}
The results of a paired-samples t test yield the following information: M = 7, s = 4.50. What is the calculated effect size? 0 0.56 0.64 1.56
1.56
The Six Steps of Hypothesis Testing
1.Identify the populations, distribution, and assumptions, and then choose the appropriate hypothesis test. 2.State the null and research hypotheses, in both words and symbolic notation. 3.Determine the characteristics of the comparison distribution. 4.Determine the critical values, or cutoffs, that indicate the points beyond which we will reject the null hypothesis. (0.05 AKA 5%) 5.Calculate the test statistic. 6.Decide whether to reject or fail to reject the null hypothesis.
Which of the following was NOT discussed in your text as an important component of conducting a meta-analysis? Collect new data to fill in gaps from previous studies. Locate all studies that have been conducted on the topic. Calculate an effect size for every study. Specify exact topic of interest before beginning.
Collect new data to fill in gaps from previous studies.
z table
Provides percentage of scores between the mean of distribution and a given z score. The full table includes positive z statistics from 0.00 to 4.50. The negative z statistics are not included because all we have to do is change the sign from positive to negative. Remember, the normal curve is symmetric: One side always mirrors the other. See Appendix B.1 for the full table.
Mdiff
really large (very significant) or really small (likely just a random chance) If μdiff = 0, then t will be really large or small
z test results allow us to:
reject the null hypothesis and accept the alternative/research hypothesis, or fail to reject the null hypothesis
In a paired-samples t test, Cohen's d, the effect size, is a measure of:
the change in the population due to the independent variable compared to the typical variability found in the population.
statistcally significant
when the data differ from what we would expect by chance if there were in fact no actual difference
Under what conditions is it permissible to proceed with a hypothesis test, even though the assumption that the population distribution is approximately normal is violated?
when the sample size is at least 30
As the sample size decreases, the t distributions get: wider. more accurate. narrower. more reliable.
wider
To determine a person's percentile rank, you first need to convert that person's raw score to a: median. formal score. normalized score. z score.
z score
To determine a person's percentile rank, you first need to convert that person's raw score to a: median. formal score. normalized score. z score.
z score
To compare a group mean with a population mean, you compute a: difference score. raw score. z score. z statistic.
z statistic???
The numerator of the ratio for calculating all the t statistics contains:
a difference between means.
μ
mean of the population
M
mean of the sample
Performing a z test involves comparing a(n):
mean to a distribution of means. {NOT score to a distribution of scores.}
The comparison distribution in a paired-samples t test is a distribution of: scores. differences between means. mean difference scores. means.
means? {NOTdiffbetweenmeans}
cohen's d
measure of effect size that assesses the difference between two means in terms of standard deviation (NOT standard error)
When creating a 95% confidence interval for a sample mean used in a z test, you look up the z-value cutoffs for the _____ of the distribution. upper 5% middle 95% lower 5% middle 5%
middle 95%
What does the term "statistically significant" mean in a test of hypothesis?
not likely to happen due to chance
A _____-tailed z test is used when the study is that the mean will be higher or lower than that of the population.
one
When we calculate the 95% confidence interval:
one value should be above the sample mean, and one value should be below the sample mean.
Mehl (2007) published a study in the journal Science reporting the results of an extensive study of 396 men and women comparing the number of words uttered per day by each sex. If he were testing the idea that women talk more than men do, what type of hypothesis test would Mehl conduct? percentile test one-tailed two-tailed nonparametric
one-tailed
A researcher hypothesizes that there is a significant relationship between stress and fatigue. Specifically, he hypothesizes that, as stress increases, fatigue levels will also increase. This example best illustrates what type of hypothesis test? null hypothesis test one-tailed test two-tailed test non-directional test
one-tailed test
Type II error
part of overlap between the 2 distributions
A one-tailed z test is used when the study will show that the mean will be higher or lower than that of the:
population
The effect size is calculated using the _____ standard deviation instead of the population standard error.
population
Which of the following values is NOT used to calculate a confidence interval for a single-sample t test? critical t value population mean standard error sample mean
population mean
Type II error + power
probability = 1
The p level is the:
probability with which a test statistic would occur if the null hypothesis were true.
Z table
provides percentages of scores between the mean and a given z score
benefits of standardization
allows fair comparisons
Another name for a p level is a(n):
alpha level {NOT z score}
In a test of significance, one would typically want to find evidence for the _____ hypothesis.
alternative/research
t test
applies when we have 2 samples Z applies with 1 sample
assumption
characteristic that we ideally require the population from which we are sampling to have so that we can make accurate inferences
paired-samples t test
compares 2 means for a within-groups design, a situation in which every participant is in both samples "dependent-samples t test" Measures twins, matching subjects, or same person (most common)
One way to increase statistical power is to _____ standard deviation.
decrease
A paired samples t test is also known as a:
dependent samples t test
p level
"alpha" the probability used to determine the critical balues ("cutoffs") in hypothesis testing
t score equation
(M-μ) / Sm
Cohen's d equation
(M-μ) / σ
CHAPTER 8
CHAPTER EIGHT PROBLEMS
What is the difference between the z and t tests?
The t test uses the estimated standard error while the z statistic uses the actual standard error of the population of means.
effect size
indicates the size of a difference and is unaffected by sample size estimated by cohen's d
converting Zcrit into raw score
+/- zcrit x (standard error) + mean
z test used when:
we know the population mean and the standard deviation
Monica has just taken a statistics exam, and she wants to calculate a 99 percent confidence interval to represent the scores in her class. What are the z statistics that fall at each line marking the middle 99 percent of scores in the distribution?
+/−2.57
two-tailed test
- A hypothesis test in which the research hypothesis does not indicate a direction of the mean difference or change in the dependent variable, but merely indicates that there will be a mean difference - Much more common
A sample from 16 shortstops was obtained in an effort to determine whether shortstops have higher salaries than other players. The mean salary (in millions of dollars) for shortstops was 1.95. Assume that the population mean for all baseball players was 1.85 and the population standard deviation was 1.61. What is the 95% confidence interval for these data? (-8.21, 5.11) (1.16, 2.74) (1.61, 1.95)
(1.16, 2.74)
Suppose you wanted to test the effects of the herbal supplement Echinacea on the length of colds. You decide to infect 10 willing participants with the rhinovirus that causes the cold, and you then give them Echinacea daily. Suppose you know that colds typically last 204 hours with a standard deviation of 36 hours. After collecting all of your data, you find that the average length of colds for your sample was 198 hours (although unlikely, assume that we were somehow able to determine the exact moment that a cold begins and ends). Which of the following would provide the z statistic for this problem?
(198 - 204) / (36 / square root of 10)
Z observed equation
(M-μ) / σm
Z score equation
(X-μ) / σ
**CHAPTER 7
**CHAPTER SEVEN PRACTICE PROBLEMS
converting Tcrit into raw score
+/- Tcrit x (Sm) + M
one-tailed test
- A hypothesis test in which the research hypothesis is directional, positing either a mean decrease or a mean increase in the dependent variable, but NOT both, as a result of the independent variable - Rarely seen in the research literature; they are used only when the researcher is absolutely certain that the effect cannot go in the other direction or the researcher would not be interested in the result if it did. - Used when the study is that the mean will be higher or lower than that of the population
Breaking assumptions
- Usually OK to not have the DV be a scale measurement, if the data are not clearly nominal or ordinal - OK to have participants not randomly selected, if we are cautious about generalizing - OK to have population distribution not normal, if the sample includes at least 30 scores
Parametric test assumptions
- dependent variable is on a scale measurement - participants are randomly selected - population distribution is approx. normal
The critical value(s) associated with a p level of 0.05 for a one-tailed hypothesis test using the z statistic is/are: -1.65 and +1.65. +1.65. +1.96. -1.96 and +1.96.
-1.65 and +1.65.
The critical value(s) associated with a p level of 0.05 for a two-tailed hypothesis test using the z statistic is/are: +1.65. -1.96 and +1.96. +1.96. -1.65 and +1.65.
-1.96 and +1.96.
benefits of sketching the normal curve
-Stays clear in memory; minimizes errors -Provides practical reference -Condenses the information
μdiff
0 is null hypothesis has no difference if research shows "drug" is not effective
The bounds of a 95 percent confidence interval for a paired-samples t test are the same as the cutoffs used to evaluate the statistical significance of a two-tailed paired-samples t test with a p level of: 0.95. 0.99. 0.05. 0.01.
0.05
What proportion of a normal distribution corresponds to z scores greater than +1.02? 0.8461 0.3461 0.3078 0.1539
0.1539
The scores of a sample are as follows: 4, 5, 8, 3, 7. The population mean is 6.54 and the population standard deviation is 2.33. Calculate the Cohen's d value for this study. 0.49 0.64 0.36 1.14
0.49
Mensa is a society for "geniuses." One way to qualify for membership is having an intelligence quotient (IQ) of at least 2.5 standard deviations above average. IQs are approximately normally distributed, according to the WAIS scale. What percentage of people will qualify to be Mensa members?
0.62%
A research study with N = 20 has an M = 4.86, μM = 4.54, and an s = 1.90. What is the t statistic? 0.75 0.17 -0.75 1.33
0.75
How to calculate a percentage for a mean of a sample
1. convert to a z statistic using the calculated mean and standard error (SDx/square root of N) 2. determine the percentage below this z statistic using the z table
What are the three assumptions for hypothesis testing?
1. dependent variable is measured on an interval or ratio scale 2. participants are randomly selected 3. population distribution is approximately normal
Roberta scored in the 85th percentile on a standardized test of reading ability. What is Roberta's associated z score? -1.04 2.3 3.1 1.04
1.04
What is the effect size for a paired-samples t test in which the mean difference score for 14 participants is 7.02 and the sum of squares for the difference scores is 117.0? 0.06 0.78 2.34 2.42
2.34
If we know the percentage of scores falling between the mean and a z score of +0.98 is 33.65%, then what is the percentage of scores falling between the mean and a z score of -0.98? -33.65 % 33.65 % 67.30 % -67.30 %
33.65%
If we know the percentage of scores falling between the mean and a z score of +0.98 is 33.65%, then what is the percentage of scores falling between the mean and a z score of -0.98? -33.65 % 33.65 % 67.30 % -67.30 %
33.65%
If Laura received a z score of 1 for her performance on a standardized math test, what percentage of scores are between Laura's z score and the mean? 34.13% -34.13% 84.13% -84.13%
34.13%
If the student newspaper reported "51% of students support the move to 4-day-a-week classes with a margin of error of 4%," which of the following would represent the interval estimate? 47% to 55% 51% 51% to 55% 4% to 51%
47% to 55%
In a standardized z distribution, the percentile rank associated with z = 0 is _____%.
50
It is known that the population mean for the verbal section of the SAT is 500 with a standard deviation of 100. In 2006, a sample of 400 students taking the SAT, whose family income was between $70,000 and $80,000, had a verbal SAT score of 513. The 95% confidence interval for this group is _____. 503.20, 522.80 513 500 492.20, 511.80
503.20, 522.80
In 2006, a sample of 400 students, whose family income was between $70,000 and $80,000, had a verbal SAT score of 513. The point estimate of the mean for the population based on this sample is _____. 487, 526 487, 513 513 500
513
If Laura received a z score of 1 for her performance on a standardized math test, approximately what percentage of scores is below her score? 34.13% -34.13% 84.13% -84.13%
84.13%
The quantitative subtest of the Graduate Record Exam (GRE) has a mean of 500 and a standard deviation of 100. What is the percentile rank for a student with a score of 650? 56.68 93.32 6.68 43.32
93.32
Vivian got a 550 on the analytical portion of the Graduate Record Exam (GRE). If GRE scores are normally distributed and have mean μ = 600 and standard deviation s = 30, what percent of students would score better than Vivian did?
95.25
Assume that the critical values for the accompanying test are 2.00. Which statements would be TRUE?
A calculated t value larger than +2.00 or smaller than -2.00 would indicate that we should reject the null hypothesis.
As with a z test, _____ can be used as a measure of effect size for a paired-samples t test.
Cohen's d
CHAPTER 9
CHAPTER NINE PROBLEMS
What is the correct formula for calculating effect size for a single sample t test?
Cohen d = (m - pop M) / s
Significance
DOESNT = big it = difference
If our critical value for t is 2.015 and our calculated test statistic is 2.012, what should we conclude?
Fail to reject the null hypothesis.
The label on the can of a particular brand of extra-large olives states that there are about 33 olives in each can. A gourmet cook feels that the claim of 33 olives per can is too high and that the average number of olives per can is less than 33. He samples 35 cans and finds M = 32.9. Assume that the p value is 0.119 for testing H0: μ = 33 versus H1: μ < 33. Are these results statistically significant?
No, they are not because the p value obtained is greater than 0.05.
Standard error (σm) equation
S / (square root of N)
corrected standard error (Sm) equation
S / (square root of N)
Consider the concept of converting a given percentile to a raw score for a student who scored in the 63rd percentile. 13% corresponds to the associated percentage that results from subtracting the area below the mean from the 63rd percentile. In what column on the z table do we look to find the associated z scores? First Second Third Fourth
Second
A researcher is interested to find the effects of humor on memory, so she randomly assigns 16 participants to either the humor group or the no-humor group. The humor group reads humorous sentences and the no-humor group reads non-humorous sentences. On a later memory test, the researcher finds that, in terms of the direction of the means, the humor group had better memory than the no-humor group, but this effect was not significant. What might you recommend that this researcher do?
She can increase her sample size to increase her power, as the effect looks as though it is barely missing significance, and her sample size is fairly small.
Corrected standard deviation (S) equation
Square root of [sum of (X-M)^2] / N-1
Suppose that one performed a paired-samples t test on a group of 30 individuals and calculated a t statistic of 1.09. What must be true about the effect size of this experiment?
The effect size must be positive and less than 1.09.
The label on the can of a particular brand of extra-large olives states that there are about 33 olives in each can. A gourmet cook feels that the claim of 33 olives per can is too high and that the average number of olives per can is less than 33. He samples 35 cans and finds M = 32.0 with a p value of 0.119 for testing H0: μ = 33 versus H1: μ < 33. What is a correct interpretation of this p value in this context?
The p value is the probability of observing a sample mean less than or equal to 32.9 olives, assuming that the true mean number of olives per can is 33 or more olives.
A researcher tests the effects of playing action video games on the spatial cognitive skills in the elderly. The researcher decides to use a directional hypothesis. What does this mean?
The researcher will predict that the video games will either improve or impair spatial cognition but not both.
A study assessed whether the attachment relationships between adolescents and their parents change as a result of a residential wilderness treatment experience for the adolescents. Participants completed the Adolescent Attachment Questionnaire at the start and at the end of the wilderness program. Which of the following would be the null hypothesis for this study?
There will be no difference in attachment relationships after the wilderness experience.
How are sample size and degrees of freedom related in a single-sample t test?
They are directly related—as sample size increases, so do degrees of freedom.
What type of hypothesis testing will the hypothesis statement, "the mean in population 1 is lower than that of the mean in population 2," require? How can this hypothesis be written in symbolic form?
This statement will require a one-tailed test. H1 : μ1 < μ2
Increasing power
^ effect size ^ sample size ^ significance level Manipulating independent variable (exaggerate mean difference between levels) One-tailed tests Decreasing the standard deviation
The researchers asked whether a dog wags its tail in a preferred direction in response to positive stimuli and in another direction in response to negative stimuli. To answer their question, they recruited 30 dogs that were family pets. Filming each dog from above, they allowed it to view (through a slat in its cage) three positive stimuli separately, in order of descending positivity: its owner, an unfamiliar human, and a cat. All the dogs responded by wagging their tails to the right. But when the dogs were presented with an unfamiliar, aggressive dog, a negative stimulus, all the dogs wagged their tails to the left. The research hypothesis for this study is that:
a dog's tail will wag differently in response to positive stimuli than to negative stimuli.
Cohen's d is:
a measure of effect size that assesses the difference between two means in terms of standard deviation.
It is hypothesized that there will be a significant difference in aggression scores after caffeine consumption. This hypothesis best illustrates what type of t test?
a paired samples t test
point estimate
a summary statistic from a sample that is just one number used as an estimate of the population parameter confidence interval NOT favored
The z statistics for the lower and upper ends of the 95% confidence interval:
are always the same.
As sample size decreases, the shape of the t distribution:
gets progressively wider.
critical values
values on the z distribution that allow us to verify statistical significance generally 0.05 or 5.00% or z=1.645
What falls within the 95% confidence interval?
an estimate that would include the population mean 95% of the time when repeatedly sampling from a population
A confidence interval is:
an interval estimate that would include the population mean a certain percentage of the time if one had repeatedly sampled from the same population.
interval estimate
based on a sample statistic and provides a range of plausible values for the population parameter confidence interval Favored
According to your text book, all of the following are steps involved in calculating a single sample t test except: identify the populations, distribution, and assumptions calculate z scores state the H0 and H1 determine the critical values/cutoffs
calculate the z scores
Suppose you wanted to test the effects of the herbal supplement Echinacea on the length of colds. You decide to infect 10 willing participants with the rhinovirus that causes the cold, and you then give them Echinacea daily. The average number of hours ill is compared with the known population mean. The z statistic based on your sample is -0.53. If you conducted a two-tailed test with a p level of 0.05, you should:
fail to reject the null hypothesis.
The difference between the denominator of the z test and that of the single-sample t test is that: in the t test, we divide by the actual population standard error (sigmaM), but in a z test, we divide by the estimated standard error (sigmaM). in the z test, we divide by the actual population standard error (sigmaM), but in a t test, we divide by the estimated standard error (sigmaM).
in the z test, we divide by the actual population standard error (sigmaM), but in a t test, we divide by the estimated standard error (sigmaM).
Statistical significance
increased when the sample size increases increased causes a decrease of standard error harder to get with two-tailed test
Increasing sample size: decreases the likelihood that we will reject the null hypothesis. increases the likelihood that we will reject the null hypothesis. has no effect on the likelihood of rejecting the null hypothesis. makes it more likely that we will make a Type II error.
increases the likelihood that we will reject the null hypothesis.
t statistic
indicates the distance of a sample mean from a population mean in terms of the estimated standard error
parametric test
inferential statistical analysis based on a set of assumptions about the population
nonparametric test
inferential statistical analysis that is NOT based on a set of assumptions about the population
confidence interval
interval estimate based on a sample statistic includes the population mean a certain percentage of the time if the same population is sampled from repeatedly 95% accuracy
A light bulb manufacturer wants to ensure that the mean lifetime of a light bulb is 500 hours. If the testing program proves that the mean lifetime of a bulb is only 125 hours, which is in the critical region, the null hypothesis:
is rejected???
The larger the effect size, the: smaller is our test statistic. more two distributions overlap. less two distributions overlap. larger is our sample size.
less two distributions overlap.
When one chooses to use a paired-samples design, it is because the parameter of interest is the population _____ difference in the responses between the two groups receiving the treatments.
mean
The mean weight for babies in the United States is 7.5 lbs. with a standard deviation of 1.25 lbs. A nurse suspects that babies at her hospital are different than the rest of the population. She takes a sample and finds that the z statistic associated with her sample is 2.5. If she is using a two-tailed test with a p level of 0.05, what decision should she make regarding the outcome of the hypothesis test?
reject the null hypothesis???
Statistical power can be defined as:
rejecting H0 when it is false.
H(1)
research/alternative hypothesis
If one finds the percentage of scores above a given z score, the normal distribution should be shaded to the _____ of the z score.
right
The correct formula for standard error of a sample size of 5 with a corrected standard deviation of 2.97 is:
s(M) = 2.97 / (square root of 5)
When calculating a confidence interval for a paired-samples t test, what value should be at the center? population mean difference sample mean difference population mean standard error
sample mean difference
A group of researchers wanted to know if there was a difference in the average yearly income taxes paid by the residents of two very large cities in the Midwestern United States. The average was $6,505 for the first city and $6,511 for the second city. The difference provided a p level of 0.0007. The difference is _____ because the p level is small.
significant
A research study has an M = 4.86, μ = 4.54, and an s = 2.10. Is this effect size large, medium, or small?
small (0.15238)
The formula for the confidence interval using a z distribution is as follows: ±z(sM) + Msample. Here sM represents _____?
standard error
The measure of variability used when calculating a confidence interval based on the z statistic is _____.
standard error
Which of the following will impact the width of the confidence interval for a paired-samples t test? standard error sample mean difference between the sample means population mean
standard error
Zobs > Zcrit
statistically significant reject null hypothesis
meta-analysis
study that involves the calculation of a mean effect size from the individual effect sizes of many studies
difference score
subtracting a sample mean from another sample's mean
deviation score
subtracting the population mean from each score
When we know the population mean, but not the population standard deviation, which statistic do we use to compare a sample mean with the population mean? µ z F t
t
What is the correct formula for a t statistic?
t = (m - Mm) / s(m)
Unnithan, Houser, and Fernhall (2006) were interested in whether playing the game Dance Dance Revolution (DDR) affected the heart rate of overweight adolescents differently than it did non-overweight adolescents. Twenty-two adolescents, 10 classified as overweight and 12 as not overweight, played DDR for 12 minutes, while the researchers measured each participant's heart rate. On average, the researchers found no difference between the heart rate of the two groups. The research hypothesis for this study is that:
the heart rate of the overweight group and the non-overweight group will differ after both groups play Dance Dance Revolution.
degrees of freedom
the number of scores that are free to vary when we estimate a population parameter from a sample (N-1) corrects standard deviation
Which of these is a way to increase statistical power? increasing standard deviation decreasing alpha decreasing sample size using a one-tailed test rather than a two-tailed test
using a one-tailed test rather than a two-tailed test
It is more difficult to reject the null hypothesis when: using a single-sample t rather than an independent-samples t. using a two-tailed test rather than a one-tailed test. you have paired-samples t rather than an independent-samples t. you have a larger as opposed to a smaller sample size.
using a two-tailed test rather than a one-tailed test.
As the sample size increases: the standard error increases. the size of our test statistic increases. the size of our test statistic decreases. the population mean increases.
{NOT Sm inc.; NOT test stat dec.)
Identify the formula for the paired-samples t test.
{NOT(Mx-My)/Sdiff)}
When Cohen's d is large (based on Cohen's conventions), the amount of overlap between the two distributions being compared is _____. 53% 80% 67% 15%
{NOT80;NOT67}
Other things being equal, a larger sample size will _____ effect size. have no effect on increase decrease increase the variability of
{NOTincrease}
Effect sizes rely on comparison of a distribution of _____ rather than on a distribution of _____ and are therefore unaffected by sample size. means; scores residuals; errors errors; residuals scores; means
{NOTm;s}
The difference in the calculation of standard error for the z and t statistics results in the t statistic being _____ than the z statistic. more accurate more reliable larger smaller
{NOTmoreaccurate}
The method for calculating s will result in a _____ value as compared with SD. more accurate smaller larger more negative
{NOTmoreaccurate}
