PY 211 Final
Which of the following is the best explanation for why the standard deviation is almost always reported with the mean?
The standard deviation measures the spread of scores from the mean, so it is important to know both the mean and the standard deviation.
Which characteristic of a histogram implies that it summaries continuous data?
The vertical bars touch at the upper boundary of each interval.
A researcher computes a test statistic and finds that the p value for this test is .03. What does this result mean?
There is a 3% likelihood of obtaining the test statistic value, if the null were true.
The ______ is the middle value in a distribution of scores that are listed in numeric order.
median
A professor compares scores on a competency exam among students at two times during a single semester. What type of t test is most appropriate for this study?
related-samples t tests
A researcher records 17 scores. What is the median position of these scores?
the 9th score in numeric order
A researcher finds that 12% of participants make between three and five visits to a physician each year. What are the real limits for this interval?
2.5-5.5
A researcher computes a one-way within-subjects ANOVA in which k = 3 and n = 10. What is the critical value for this test at a .05 level of significance?
3.55
A researcher records the time in seconds it takes a sample of participants to walk alone through a dark portion of campus. The researcher computes SS = 1,200. Assuming that a sample of 25 participants was observed in this study, what is the standard deviation for these data?
7.1 s
How is the sample variance computed differently from the population variance?
The calculation in the denominator is different.
Regardless of the distribution of the population, the sampling distribution of sample means will be approximately normally distributed. What characteristic of the mean explains this?
central limit theorem
As sample size increases, the standard error of the mean ______.
decreases
One difference between a repeated-measures design and a matched-samples design is that ______.
only one design involves observing the same participants in each group
Which of the following distributions has the largest variability?
scores: 1, 3, 6, 9, and 12
A researcher conducts a study in which k = 4 and n = 22 in each group. What are the degrees of freedom for the one-way between-subjects ANOVA?
(3, 84)
An article states that a sample of 40 participants took 12 ± 2.3 (M ± SEM) s to complete a cognitive assessment. Which value is the standard error of the mean?
2.3
"Elementary school children spent significantly more time reading the presence of a teacher than when the teacher was absent, t(7) = 2.804, p < .05 (mc044-1.jpg =?4 0.46)." In this related-samples t test, how many participants were observed?
8
What does it mean to say that the sample mean is an unbiased estimator of the population mean?
If we select a sample at random, then on average we can expect the sample mean to equal the population mean.
A biopsycholofist studies the role of the brain chemical serotonin in aggression ( I.e., whether the chemical will lower aggression levels). One sample of rats serves as a control group and receives a placebo. A second sample of rats receive a drug that lowers brain levels of serotonin. Then the researcher tests the animals by recording the number of aggressive responses each of the rats display and comparing the means from each group.
Two Independent Samples t Test: Two samples (rat given serotonin, control group of rats not given serotonin), independent samples (different rats in each group), IV = group (given serotonin, control); DV= number of aggressive responses
A researcher randomly selects a sample of athletes and reports that their average score on a health and fitness scale is 23. Based on the characteristics of the sample mean, what does this say about the mean in the population?
We expect that the population mean is equal to 23 because the sample mean is an unbiased estimator of the population mean.
Following a significant one-way between-subjects ANOVA in which k > 2, what is the next appropriate step?
conduct post hoc tests
A researcher reports that mean ratings of liking for some food are 0.8 ± 2.4 (M ± SD). If the null hypothesis was that the mean equals 0, then what is the effect size for this test using estimated Cohen's d?
d = 0.33; medium effect size
A health practitioner measures the heart rate (in number of beats per minute) of patients under low, moderate, and high stress levels. Heart rate can be best described as ______.
discrete data
A key difference between a t statistic and a z statistic is that the standard error is ______ to compute a t statistic.
estimated
Statistical analysis allows researchers to ______.
evaluate scientific observations
A researcher finds that the average preschool-aged child drinks two cups of milk per day. Assuming these data are normally distributed, the z score for the average cups per day in this example is ______.
exactly equal to 0
A therapist observes that spouses are more likely to forgive their partners for lying to them if they find out the truth from their spouse and not a third party. In this example, the dependent variable is ______.
forgiveness
Procedures that allow researchers to infer or generalize observations made with samples to the larger population from which they were selected best describes ______.
inferential statistics
The range of scores between the upper and lower quartiles of a distribution is called the ______.
interquartile range
Grouped data are distributed into ______, whereas ungrouped data are distributed into ______.
intervals; categories
A researcher asks a sample of brothers and sisters to rate how positive their family environment was during childhood. In this study, the differences in ratings between each brother and sister pair were compared. The type of design described here is called a ______.
matched-samples design
State the four scales of measurement in order from least informative to most informative.
nominal, ordinal, interval, ratio
A movie critic ranks a movie on a scale from 1 (lowest) to 4 (highest) stars. What scale of measurement are the ratings?
ordinal
______ data describe numeric aspects of phenomena; whereas ______ data describe nonnumeric aspects of data.
quantitative; qualitative
A researcher computes the following one-way between-subjects ANOVA table. State the decision at a .05 level of significance. (Hint: Complete the table first.)
reject the null hypothesis
Which of the following describes a descriptive statistic?
summarize
The normal distribution has all of the following characteristics, except that ______.
the total area under the curve is greater than 1.0
Regardless of the number of scores in a distribution, the range only includes ______ score(s) in its calculation.
two
A researcher compares differences in mean health scores between students at two local high schools. Assuming that the population variance is unknown, what type of t test is appropriate for this study?
two-independent-sample t test
A researcher records the level of attention among 18 students during an interactive and lecture portion of a single class. If she computes a related-samples t test at a .05 level of significance (two-tailed test), then what are the critical values for this test?
±2.110
State the critical value(s) for a t test using a two-tailed test at a .05 level of significance: t(20).
+/- 2.093
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 s or less?
1660
The following is a simple frequency distribution table. If we convert this frequency distribution to relative percentages, which of the following gives the corresponding relative percentages in each interval listed from the top down? Interval frequency 44-46 6 41-43 4 38-40 5 35-37 10 32-34 5 =30
20%, 13%, 17%, 33%, 17%
A researcher selects a sample of 100 participants from a population with a mean of 38 and a standard deviation of 20. About 68% of the sample means in this sampling distribution should be between a sample mean of ______.
36 and 40
The t distribution is similar to the z distribution except ______.
ALL OF THESE a. it is associated with greater variability b. it is characterized by "thicker" tails compared with the z distribution c. it is associated with scores being more likely in the tails of the distribution
In terms of characterizing samples, statistical theory was developed using a sampling strategy in which ______.
ALL OF THESE a. the order of selecting participants matters b. the same participant can be selected twice in the same sample c. participants are replaced after being sampled
A researcher wants to know whether there is a relation between the average number of guns in a household and crime rate (per 100,00 population). The researcher looks up the crime rate for different states (per 100,000 population), and then sneaks a survey to a resident of each state to find the average number of guns per household in that state.
Correlation: One sample (oddly, the states are the sample), two measures per state (average number of guns in the household and crime rate per 100,000 population), no IV, DV1 = number of guns in household, DV2= crime rate.
A psychologist would like to determine whether there is a consistent relationship between verbal skills as measured by the Scholastic Achievement Test (SAT) and performance on an anagram task. (Anagrams are words with the letter scrambled. The task is to unscramble the letters and identify the word.) The researcher retrieves the SAT score for each student (with permission of the student) and then each participant is given a set of anagrams. The psychologist records how much time is needed to solve them. Then, the relation between SAT scores and anagram performance is tested.
Correlation: One sample (students), two measures per person (SAT score, performance on anagram test), no IV, DV1= SAT score; DV2= performance on anagram test
A researcher reports that the size of an effect in some population is d = 0.88. Which of the following is an appropriate interpretation for d?
Mean scores shifted 0.88 standard deviations in the population.
A researcher measures the amount of coffee consumed by college students while studying during the final exam week. In her study, she found that students drink 2.3 ± 0.8 (M ± SD) cups of coffee per study session. Assuming the data are normally distributed, which of the following is the most appropriate conclusion?
Most students drink between 1.5 and 3.1 cups of coffee per study session.
The size of a population is symbolized as ______, whereas the size of a sample is symbolized as ______.
N;n
A researcher records a sample of 30 exam scores and finds that if these data were treated as a population, that the population variance calculation for these data is larger than the sample variance calculation for these same data. Is this outcome for variance possible?
No, the sample variance will be larger because SS is divided by degrees of freedom in the denominator of the variance formula.
Two normal distributions are observed. The first distribution has a mean of 12 and a standard deviation of 2. The second distribution has a mean of 0 and a standard deviation of 2. For which distribution will the z score for the mean be larger?
None, the z score will be the same.
A psychologist would like to know whether the change in seasons has any consistent effect on people's mood. In the middle of each of the four seasons the psychologist selects a random sample of n= 10 students. Each individual in the different samples is given a standardized mood/depression questionnaire.
One way analysis of variance (ANOVA): more than two samples (students in spring, summer, fall, and winter), one measure per person (score on mood/depression questionnaire), IV= season (spring, summer, fall, and winter), DV= score on mood questionnaire
A nutrition store in the mall is selling "memory booster" which is a concoction of herbs ad minerals that is intended improve memory performance. To test the effectiveness of the herbal mix, a researcher obtains a sample of n= 16 people and has each person take the suggested dosage each day for 4 weeks. At the end of the four weeks period, each individual takes a standardized memory test. The scores from the sample produced a mean of M= 24. In the general population, the standardized test is known to have a mean of µ= 20
Single Sample t test: One sample (16 people), one measure per person (performance on memory test), know population mean (=20) but not population standard deviation, IV= beer (craft, commercial; DV= rating on taste scale
A local brewery believes that they have crafted a beer that is far superior to a commercial brand. People have consistently rated the commercial brand of beer a mean of µ= 6 on a 1-10 point scale. A sample of thirty people is obtained and each person tastes and rates the craft beer on the 1-10 point scale. The mean rating from this sample is compared to the population mean.
Single Sample t test: One sample (30 people), one measure per person (rating on taste scale), know population mean (=6) but not population standard deviation, IV = beer (craft, commercial; DV= rating on taste scale
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.
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.
In hypothesis testing, a researcher can never ______.
The null hypothesis always makes statements about a population parameter.
A researcher studies the effect of two practice methods on memory. A sample of n= 30 subjects memorizes a list of nonsense syllables (e.g., ZOK) using method A. During a recall test, the number of errors are recorded. Then each subject repeats the procedure using a new practice method B and new nonsense syllables; again, the number of errors are recorded. The researcher wants to know whether there is a difference in memory scores for method A and method B.
Two Related Samples t Test: One sample (30 subjects), two measures per person (memory score with Method A, memory score of Method B), IV= practice method (A,B); DV=memory score
A statistics instructor would like to know whether it is worthwhile to require students to do weekly homework assignments. For one section of the statistics course, homework is assigned, collected, and graded each week. For another section, the same problems are suggested each week, but the students are not required to turn in their homework. At the end of the semester, students from both classes take the same final exam and the performance on the exam is compared.
Two independent Samples t test: Two samples (two sections of students), one measure per student (exam performance); independent samples (different sections of students), IV= section (required homework, recommended homework), DV= performance on exam
After a sample of n= 25 high school students took the SAT, took a special training course for the SAT, and then took the SAT again. Their SAT scores averaged M= 18 points higher after the course than before the training course.
Two related Samples t Test: One sample (25 high school students), 2 measures per subject (before and after treatment, repeated measures), IV= time (before, after); DV= SAT score
A researcher records the following data for how participants rated the likability (on a scale from 1 = not liked at all to 7 = very likable) of an individual who blushed after making a mistake: 5, 4, 7, 6, 6, 4, 6, 7, 2, 5, and 6. Is the mode equal to the median in this example?
Yes
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
Given the same set of data for a population and sample, would the mean for both data sets be equal?
Yes, this would be true anytime both data sets are the same.
A researcher investigates whether or not a new cold medication disrupts mental alertness. It is known that scores on a standardized test containing a variety of problem-solving tasks are normally distributed with µ= 64 and o= 8. A random sample of n= 16 subjects are given the drug and then tested. For this sample, the mean is M= 58.
Z test: One sample (16 subjects), one measure per subject (performance on problem solving test), know population mean (=64) and standard deviation (=8), IV= group (given drug, population); DV= performance on problem solving test
A sampling distribution of the sample mean or variance is ______.
a distribution of all sample means or sample variances that could be obtained in samples of a given size from the same population
Suppose that a researcher is interested in a group of 10 million people who paid to see a movie playing in theaters. In this example, the 10 million moviegoers would be regarded as ______.
a population of moviegoers who paid to see the movie in a theater
A distribution of all sample means or sample variances that could be obtained in samples of a given size from the same population is called ______.
a sampling distribution
In a normal distribution, 50% of all data ______.
all of the above
A researcher notes that the variability attributed to difference between group means is quite large. Which source of variation is the researcher referring to?
between-groups
A type of factor in which different participants are observed in each group, or at each level of the factor, is called ______.
between-subjects factor
When reporting the results of a one-sample z test using APA format, the ______ does not need to be reported.
critical values
A researcher reports that the mean time it takes to complete an experimental task is 1.4 ± 8.0 (M ± SD) s. If the null hypothesis was that the mean equals 1.0, then what is the effect size for this test using estimated Cohen's d?
d = 0.05; small effect size
Computing a one-way between-subjects ANOVA is appropriate when ______.
different participants are observed one time in each of two or more groups for one factor
Recording the number of dreams recalled is an example of ______ data; whereas recording the time (in minutes) spent in a dream stage of sleep is an example of ______ data.
discrete; continuous
A researcher tests whether the dosage level of some drug (low, high) causes significant differences in health. To do this, the researcher randomly assigns rat subjects to receive a low or high dosage of the drug and records health-related measures in both groups. The type of method described is ______.
experimental
Which of the following requires the calculation of a real range?
frequency distributions for grouped data
A graphical display for grouped frequency distributions with continuous data is called a ______.
histogram
A researcher measures the weight (in ounces) of newborn infants in the month of March. What type of graphical display would be most appropriate for summarizing the frequency of infants falling into different intervals of weight?
histogram
A professor compared differences in class grades between students in their freshman, sophomore, junior, and senior years of college. If different participants were in each group, then what type of statistical design is appropriate for this study?
one-way between-subjects ANOVA
Suppose you select a sample of three people from a population of four (A, B, C, D). Which of the following samples is possible using the experimental sampling strategy?
persons B, C, and D
A psychologist reviews her notes for all her patients and determines that on average her patients complete therapy in 24 days. The average time to complete therapy among all her patients is called a(n) ______.
population parameter
A researcher assigns 21 adolescents to rate the likability of a person described in a vignette as having one of three personality traits. An equal number of participants are assigned to each group. If mc005-1.jpg = 4.08 for this study, then what was the decision at a .05 level of significance for a one-way between-subjects ANOVA?
reject the null hypothesis
A researcher compares the difference in the amount of texting by students in class during the first week and last week of classes. The type of design described here is called a ______.
repeated-measures design
The ______ is an inferential statistic used to determine the number of standard deviations in a t distribution that a sample mean deviates from the mean value or mean difference stated in the null hypothesis.
t statistic
A researcher identifies college students as a group of interest to test her hypothesis. She then identifies a few local college students and selects a small group of the local college students to be observed. In this example, the sample is ______.
the small group of college students who here observed
A researcher obtains z = 1.45 for a one-sample z test. What is the decision for this test at a .05 level of significance?
to retain the null hypothesis
A researcher conducts a study measuring differences in brain activity among rats placed on either a continuous or intermittent reward schedule. Assuming that the population variance in unknown, what t test is appropriate for this study?
two-independent-sample t test
