Psy Final
What is indicated by a Pearson correlation of r = +1.00 between X and Y?
Each time X increases, there is a perfectly predictable increase in Y.
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.
A treatment is administered to a sample of n = 9 individuals selected from a population with a mean of µ = 80 and a standard deviation of σ = 12. After treatment, the effect size is measured by computing Cohen's d, and a value of d = 0.50 is obtained. Based on this information, what is the mean for the treated sample?
M=86
null hyothesis
RR/OR = 1, RD = 0 - no association in the population
For a group of graduating college seniors, a researcher records each student's rank in his/her high school graduating class and the student's rank in the college graduating class. Which correlation should be used to measure the relationship between these two variables?
Spearman correlation
Assuming all other factors are held constant, if the df value for a two-tailed t test with α = .05 were increased from df = 6 to df = 20, what would happen to the critical values for t?
The critical values would move closer to t = 0.
Which statement below is not consistent with the distribution of sample means?
The distribution of sample means tends to pile up around the population standard deviation.
A researcher completes a hypothesis test using a = .05. Based on the evidence from the sample, the researcher decides to reject the null hypothesis. Which statement below is true?
The researcher might have made a Type I error, but the probability is less than 5%.
The results of a hypothesis test are reported as follows in a scientific report: t(38) = -3.13, p < .05. Based on this information, which statement below is not correct?
The sample size was n = 39.
Central Limit Theorem
The theory that, as sample size increases, the distribution of sample means of size n, randomly selected, approaches a normal distribution.
Delores must grade a driver's test completed by a group of training students. She knows that driver's test scores are normally distributed with µ = 50 and σ = 6. Students are required to score in the top 75% of students on the test in order to pass the test and continue on with the training course. Which score do students need to obtain at a minimum in order to pass the test and continue with the course?
X= 46
A researcher measures driving distance from college and weekly cost of gas for a group of commuting college students. Which kind of correlation is likely to be obtained for these two variables?
a positive correlation
All else constant, which combination of factors would increase the width of a confidence interval most?
a smaller sample size and a larger confidence interval
Which of the following accurately describes a hypothesis test?
a statistical technique that uses the data from a sample to evaluate a hypothesis about a population
If an analysis of variance is used for the following data, what would be the effect of changing the value of M2 to 25? Sample Data M1 = 10 M2 = 20 SS1 = 90 SS2 = 70
an increase in SSbetween and an increase in the F-ratio
In an analysis of variance, differences between participants contribute to which of the following variances?
both between-treatments variance and within-treatments variance
A researcher is interested in having as much ability as possible to identify a treatment effect if one really exists. Which of the following strategies should they employ?
change the sample size from n = 25 to n = 100
Which statement below is consistent with making a Type I error?
concluding that a treatment has an effect when it really has no effect
An analysis of regression is used to test the significance of a linear regression equation based on a sample of n = 20 individuals. What are the df values for the F-ratio?
df = 1, 18
A researcher conducts a hypothesis test using a sample of n = 20 with M = 34 and s2 = 36 from an unknown population. What is the df value for the t statistic?
df = 19
Which of the following samples will have the smallest value for the estimated standard error?
n = 16 with s2 = 16
A researcher is using a two-tailed hypothesis test with α = .05 to evaluate the effect of a treatment. If the boundaries for the critical region are t = ± 2.080, then how many individuals are in the sample?
n=22
A sample is selected from a normal population with µ = 40 σ = 10. If the sample mean of M = 46 produces a z-score of z = +3.00, then how many scores are in the sample?
n=25
A researcher conducts a hypothesis test using a sample from an unknown population. If df= 30 for the t statistic and M = 46 and s2 = 10, how many individuals were in the sample?
n=31
A sample of n = 4 scores is selected from a normal population with a mean of µ = 50 and a standard deviation of σ = 20. What is the probability of obtaining a sample mean less than M = 52?
p=0.5793
Which correlation should be used to measure the relationship between gender and grade point average for a group of college students?
point-biserial correlation
Which of the following describes a typical distribution of F-ratios?
positively skewed with all values greater than or equal to zero
What is the sample variance and estimated standard error for a sample of n = 9 scores with SS = 72?
s2 = 9 and sM = 1
Consider a researcher who is conducting final clinical trials to validate that a new treatment for anxiety is effective. This researcher is extremely focused on avoiding mistakes in concluding that this new treatment is effective when it really is not when conducting their research. What should this researcher do?
set a low alpha level
If a treatment produces a sample mean of M = 25 with s = 18 among a sample of n = 36, which t-statistic should be obtained and which decision should be made if conducting a two-tailed hypothesis test with α = .05 and an expected mean of µ= 30?
t = -1.67 and fail to reject H0
With α = .05, the two-tailed critical region for a t test using a sample of n = 20 participants would have boundaries of _____.
t = ±2.093.
Which of the following results from a hypothesis test involving the computation of a t-statistic is structured correctly based on standards for presenting hypothesis tests in scientific reports?
t(19) = 2.30, p < .05, r2 = 0.42
population standard deviation
the square root of the population variance
A researcher selects a sample and administers a treatment for anxiety to the individuals in the sample. If the sample is used for a hypothesis test, what does the alternative hypothesis (H1) put forth about the treatment?
the treatment has an effect on anxiety
If a sample of n = 4 scores is obtained from a normal population with µ = 70 and σ = 12, what is the z-score corresponding to a sample mean of M = 69?
z=-0.17
For a normal population with µ = 60 and σ = 50, the distribution of sample means based on n = 25 will have an expected value of ____ and a standard error of ____.
µM = 60; σM = 10.
An instructor is interested in whether frequent feedback in their course to a small sample of students influences student performance. The instructor knows that final class scores are normally distributed with µ = 85 and σ = 6. Which is the alternative hypothesis for this research study?
µfrequent feedback ≠ 85
A researcher is interested in whether a new teaching method influences the public speaking skills of students in an introductory to communications class. The researcher knows that public speaking skills in the class are normally distributed with µ = 10 and σ = 2. Which is the null hypothesis for this research study?
µteaching method = 10
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
A vertical line drawn through a normal distribution at z = -0.75 separates the distribution into two sections, the body and the tail. What proportion of the distribution is in the tail?
0.2266
Consider that a population is normally distributed with µ= 100 and σ = 6. What is the power of a α = .05, two-tailed hypothesis test with an expected treatment of 2 points and sample size of n = 64?
0.7611
A population is normally distributed with µ = 145 and σ = 20. Which is the percentile rank for X = 171?
90.32%
standard error
An estimate of the standard deviation of the sampling distribution of a statistic.
