health 320 exam 1
As a general rule, a simple frequency distribution should have between
5 and 20 intervals
In a sample of 30 participants, a researcher estimates the 95% CI for a sample with a mean of M1-M2= 0.7 and an estimated standard error for the difference (SM1-M2) of 0.2. What is the confidence interval at this level of confidence?
95% CI 0.3, 1.1
In a sample of 28 participants, a researcher estimates the 95% CI for a sample with a mean of M = 1.5 and an estimated standard error ( Sm) of 0.3. What is the confidence interval at this level of confidence?
95% CI 0.9, 2.1
Fill in the missing values for A and B in this frequency distribution table: intervals frequency 6.0-6.6 12 5.3-5.9 7 4.6-5.2 ?? 3.9-4.5 10 ?-3.8 8 N=50
?=3.2, ??=13
Which measure of effect size is most commonly reported with a t test?
Cohen's d
A professor teaches a certain section of material using a lot of examples with sports and cars to illustrate. He is concerned that this may have biased his instruction to favor male students. To test this, he measures exam grades from this section of material among women (n = 10) and men (n = 10). The mean score in the male group was 84±4.0 (M±SD); in the female group, it was 78±8.0 (M±SD) points. If the null hypothesis is that there is no difference in exam scores, then test the null hypothesis at a .05 level of significance.
Exam scores were significantly higher in the male group, tobt (18) = 2.12, p < .05.
A researcher conditions rats to fear a tone that was sounded just prior to a brief shock. To measure fear following this conditioning, she records the number of lever presses by each rat in the presence and in the absence of the tone. It was hypothesized that reduced lever pressing in the presence of the tone was evidence for a conditioned fear response in rats. If the researcher tested this hypothesis at a .05 level of significance (two-tailed test), then what is her decision if she computes t obt= 2.842 in a sample of 8 rats.
Reject the null hypothesis; there is evidence for a conditioned fear response.
Two researchers (A and B) compute a one-sample t test. For both tests, the mean difference between the sample and value stated in the null hypothesis is 5, but the standard error is smaller for Researcher A. Which test is more likely to result in a decision to reject the null hypothesis?
Researcher A.
Two researchers (A and B) compute a one-sample t test. For both tests, the standard error is the same, but the mean difference between the sample and value stated in the null hypothesis is smaller for Researcher A. Which test is more likely to result in a decision to reject the null hypothesis?
Researcher B.
State the problem with this simple frequency distribution. intervals frequency 8-10 4 6-8 7 4-6 3 2-4 6 0-2 9
The class intervals overlap.
Two researchers analyze the same data set. Researcher A uses a two-independent sample t test and decides to retain the null hypothesis. Researcher B uses a related samples t test and decides to reject the null hypothesis. Which of the following is a likely explanation for the disparity in the decisions made.
The related samples t test had greater power to detect the effect.
The sample mean is an unbiased estimator, follows the central limit theorem, and has minimum variance.
true
A researcher records the following data for the number of dreams recalled during a night of sleep for 10 college students: 3, 2, 4, 4, 3, 1, 1, 0, 2, and 0. Is the mean equal to the median in this example?
yes
State the critical value(s) for a t test using a two-tailed test at a .05 level of significance: t(20).
±2.086
What is the percentile point at the 90th percentile in the following distribution? frequency percentile rank 9-11 100% 6-8 80% 3-5 40% 0-2 20%
10
In a sample of 18 participants, a researcher estimates the 80% CI for a sample with a mean of M1-M2= 8.8 and an estimated standard error for the difference (SM1-M2) of 1.8. What is the upper confidence limit for this interval?
11.2
The following is a simple frequency distribution table. If we convert this frequency distribution to relative percentages, which of the following gives the corresponding percentages in each interval listed from the top down. intervals frequency 44-46 6 41-43 4 38-40 5 35-37 10 32-34 5 N=30
20%, 13%, 17%, 33%, 17%
SPSS practice: A research tried to test if breakfast is important for gaining energy. He collected data from 30 students who stated had eaten breakfast on the test day from a large class with population mean 80 on the average score. Unfortunately, he could not get the variance for the population. The following is his SPSS results. [picture] Please calculate the 95% confidence interval for the sample using the information from the SPSS result?
79.24; 91.09
A researcher reports with 90% confidence that 31% to 37% of Americans believe in ghosts. What is the point estimate for this interval?
34%
A researcher computes the definitional formula for SS, as finds that ∑(x-M)2 = 44. If this is a sample of 12 scores, then what would the value of sample variance be using the computational formula?
4.0
A researcher computes the computational formula for SS, as finds that ∑x = 22 and ∑x2 = 126. If this is a sample of 4 scores, then what would SS equal using the definitional formula?
5
A researcher records the following scores: 5, 3, 7, 6, 2, 8, 0, and 1. In terms of these data, the sum of the squared differences of scores from their mean is
60
A researcher has participants rate the likability of a sexually promiscuous person described in a vignette as being male (n = 20) or female (n = 12). The mean likability ratings in each group were 4.0. If the null hypothesis is that there is no difference in likability ratings, then do likability ratings differ at a .05 level of significance?
No, this result is not significant, tobt(30) = 0
The test statistic for a related samples t test makes tests concerning a single sample of
different scores
The t distribution is similar to the z distribution except
it is associated with greater variability it is characterized by "thicker" tails compared with the z distribution it is associated with scores being more likely in the tails of the distribution
Which of the following is a type of related samples design in which different participants are actually observed in each group, but treated statistically as if they are the same persons in each group.
matched samples design
A researcher distributes frequencies into the following classes: absent, tardy, present. What type of data are distributed?
nominal data, qualitative data and ungrouped data
A researcher conducts a study in which the same participants are observed across each level of the independent variable. If there are only two levels of the independent variable, then what type of t test is appropriate for this study?
related samples t test
A type of related samples design in which participants are observed more than once is called a
repeated measures design
Two researchers (A and B) compute a two-independent sample t test. For both tests, the mean difference between the two groups is 10, but the standard error is smaller for Researcher A. Which test is more likely to result in a decision to reject the null hypothesis?
researcher A
A researcher measures deviant behavior in a sample of 12 children from abusive homes (Sample A). Another researcher measures the same behavior in a sample of 18 children from abusive homes (Sample B). Which sample is associated with larger degrees of freedom?
sample B
A(n) ________ is a sample statistic that equals a population parameter on average.
unbiased estimator
A researcher determines that students study an average of 80+20 (M+SD) minutes per week. Assuming these data are normally distributed, what is the z score for students studying 60 minutes per week?
-1
A researcher records the following response times to a visual stimulus: 23+3.1 (M+SD) seconds. Assuming these data are normally distributed, what is the probability that participants responded in 20 seconds or less?
.1660
A news poll showed that voters had no preference for either of three candidates. In this example, the probability of a vote for, say, Candidate A equals
1/3
Most behavior is believed to ________ a normal distribution.
approximate
When cumulating frequencies from the bottom up, the data are discussed in terms of
at most, less than, at or below
A research design in which different participants are observed one time in each group of a research study is called:
between subjects design
A researcher reports that the mean difference in response time to an auditory versus a visual cue is 0.83 seconds, with a pooled sample variance equal to 2.45. What is the effect size for this test using estimated Cohen's d?
d = 0.53; medium effect size
Computing a two-independent sample t test is appropriate when
different participants are assigned to each group the population variance is unknown participants are observed one time
The definitional formula ______ the computational formula for SS.
equal
The central limit theorem states that the sample mean will equal the population mean on average.
false
If a researcher selects a sample of 64 participants from a population with a variance of 16, then the standard error of the mean will be 2.0.
false; Sqrt (16/64) =1/2 =0.5
The three steps for constructing a simple frequency distribution are
find the real range, find the interval width, and construct the frequency distribution
A graphical display for grouped frequency distributions with continuous data is called a
histogram
The related samples design can ________ the power to detect an effect by making the standard error ________.
increase; smaller
Each of the following is an advantage for using the related samples design, except
it increases the variability measured in a study
To determine the interval width, we divide the ________ by the number of intervals.
real range
Which of the following distributions has the largest variability?
scores: 1, 3, 6, 9, and 12 (biggest diff b/w smallest and largest)
Which of the following is an example of a distribution with NO variability?
scores: 5, 5, 5, 5, 5, and 5
Which of the following summarizes a t test that was significant and associated with a large effect size?
t(12) = 2.95, p < .05, d = .82
A researcher records 52 scores. What is the median position of these scores?
the average of the 26th and 27th scores in numeric order
A z transformation can be computed to locate sample means in a sampling distribution.
true
If a researcher selects a sample with a mean of 8, then the mean of the sampling distribution of possible sample means will also equal 8.
true
If data are reported as 12 ± 20 (M ± SEM), then the standard error of the mean is equal to 20.
true
SPSS practice: A research tried to test if breakfast is important for gaining energy. He collected data from 30 students who stated had eaten breakfast on the test day from a large class with population mean 80 on the average score. Unfortunately, he could not get the variance for the population. The following is his SPSS results. [picture] According to this SPSS result, should the researcher draw the conclusion that eating breakfast can increase the student score, at the .05 level of confidence?
According to the p-value, .085>.05, he cannot reject the null hypothesis that population mean=80, he cannot draw the conclusion that eating breakfast can increase the student score.
A researcher reports that the time (in minutes) it takes children who are "picky eaters" to finish their vegetables is negatively skewed, with children finishing their vegetables in 4.2±1.0 (M±SD) minutes. Based on Chebyshev's theorem, we can conclude that
At least 89% of children finished their vegetables in 1.2 to 7.2 minutes.
A researcher sampled 16 couples and measured the mean difference in their marital satisfaction. Each couple was paired and the differences in their ratings (on a 7-point scale) were taken. If the mean difference in satisfaction ratings for this sample was 1.8±2.0 (Md ±Sd), then what is the decision at a .05 level of significance?
Satisfaction ratings significantly differ, tobt (15) = 3.60.
A researcher conducts two t tests. Test 1 is a two-tailed test with a smaller sample size at a .05 level of significance. Test 2 is a two-tailed test with a larger sample size at a .05 level of significance. What do you know about the degrees of freedom for each test?
Test 2 is associated with larger degrees of freedom.
he mean crying time of infants during naptime at a local preschool is 12 minutes. The school implements a new naptime routine in a sample of 25 infants and records an average crying time of 8±4.6 (M±SD) minutes. Test whether this new naptime routine reduced crying time at a .05 level of significance.
The new naptime routine significantly reduced crying time, t(24) = -4.35, p < .05.
