Psych Stats Exam 1

A population of scores has µ = 500. In this population, a score of X = 475 corresponds to z = -0.25. What is the population standard deviation?

100​

Which set of scores has the smallest standard deviation?

145, 143, 145, 147

A sample consists of n = 16 scores. How many of the scores are used to calculate the range?

2

If the participants included in this table came from a sample of 400 participants, how many participants were between the ages of 31 and 59?

274

For the population of scores shown in the frequency distribution table, the mean is ____.​ ​ X f 5 2 4 1 3 3 2 2 1 2

29/10 = 2.90

For the following distribution of quiz scores, How many individuals had a score of X = 2?​ X f 5 6 4 5 3 5 2 3 1 2 ​

3

A population has a mean of µ = 30. If 3 points are added to each score, what is the mean for the new distribution?

33

After every score in a sample is multiplied by 3, the mean is calculated and found to be M = 21. What was the mean for the original scores?

7

The interquartile range for Depression in the younger group equals

7.25

For a population with µ = 100 and σ = 20, what is the X value corresponding to z = -0.75?

85​

In Lab 1, you learned about an international study exploring the attitudes, behaviors, and beliefs of individuals from over 170 countries, collected during late March 2020 and early April 2020, when the COVID-19 pandemic was proving to be devastating all over the world. Our Lab 1 data sets were samples of Americans (USA) who completed the research survey in English. The tables and graphs provided here were obtained from a sample of Americans (USA) and Canadians, all of whom responded to the survey in English. For then next 7 questions, use the information provided in the tables and graphs provided here. Round all numerical answers to 2 decimal places. Which of the following is NOT accurate?

Anxiety scores vary more than Depression scores.

After a researcher adds 5 points to every score in a sample, the standard deviation is found to be s = 10. The original sample had a standard deviation of s = 5.

False

For a 100-point exam, a score of X = 65 is definitely above the median.

False

For the following distribution of scores, Σ X = 10.​ X f 4 1 3 2 2 3 1 2

False

It is impossible for the value of the mode to be greater than the value of the mean.

False

The maximum anxiety score for the older group is an outlier.

False

The statistics presented above were obtained from an experiment comparing different age groups.

False

According to an end of chapter problem somewhere in your textbook, people smile an average of μ = 62 times per day. with a standard deviation of σ = 18. Assuming that the distribution of smiles is approximately normal, which of the following diagrams correctly represents the proportion of people who smile fewer than 45 times per day?

Graph a.

A sample of scores has M = 50 and s = 5. If every score in the sample is multiplied by 3, then what are the new values for the mean and standard deviation?

M = 150 and s = 15

A positive deviation score always indicates a score that is greater than the mean.

True

A professor standardizes exam scores so that all exams have μ = 50 and s = 10. If the original scores from an exam have μ = 42 and s = 6, then a student with an original exam score of X = 45 would receive a standardized score of X = 55.

True

A researcher is interested in the average income for registered voters in the United States. The entire group of registered voters is an example of a population.

True

A score with a value less than or equal to the mean will have a z-score that is less than or equal to zero.

True

An operational definition identifies a set of operations for measuring an external behavior and then uses the resulting measurement as a definition of a hypothetical construct.

True

For a sample with M = 20 and s = 1, a score of X = 17 would be considered an extremely low score.

True

Under what circumstances is a score that is located 5 points above the mean a central value, relatively close to the mean?

When the population standard deviation is much greater than 5

A population of N = 10 scores has a mean of µ = 6. After one score is removed, the mean is found to be µ = 5. What is the value of the score that was removed?

X = 15

A distribution with µ = 100 and σ = 5 is being standardized so that the new mean and standard deviation will be µ = 50 and σ = 10. In the new, standardized distribution your score is X = 45. What was your score in the original distribution?

X = 97.5

In which age group was the highest depression score obtained?

Younger

If a variable's possible scores can be divided into an infinite number of fractional parts, then it is a(n) ____ variable.​

continuous

For a negatively skewed distribution with a mean of M = 20, what is the most probable value for the median?

greater than 20

A distribution of scores has a mean of µ = 50. One new score is added to the distribution and the new mean is found to be µ = 48. From this result, you can conclude that the new score was ____.

less than 50

A researcher obtains eye color from a sample of n = 50 people. Which measure of central tendency would be appropriate to summarize the measurements?

mode

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

Using letter grades (A, B, C, D, and E) to classify student performance on an exam is an example of measurement on a(n) ____ scale of measurement, and using a percentage is an example of measurement on a(n) _____ scale.

ordinal, ratio

A researcher is studying the quality of life for adults between the ages of 65 and 75 living in the 10 largest US cities. US adults in this age range constitute the ______________ of interest.

population

Based on the mean, median, and mode, the distribution of depression in the older group appears to be

positively skewed

A researcher uses an anonymous survey to investigate the study habits of American college students. Based on the set of 56 surveys that were completed and returned, the researcher finds that these students spend an average of 4.1 hours each week working on course material outside of class. For this study, the set of 56 students who returned surveys is an example of a ____, and the average of 4.1 hours each week studying outside of class is an example of a _____.

sample, statistic

The average verbal SAT score for the entire class of entering freshmen is 530. However, if you select a sample of 20 freshmen and compute their average verbal SAT score you probably will not get exactly 530. What statistical concept is used to explain the natural difference that exists between a sample mean and the corresponding population mean?

sampling error

A population distribution has σ = 6. What position in this distribution is identified by a z-score of z = -1.00?

six points below the mean

In an experiment comparing two methods for teaching social skill training to children with autism, the independent variable is ____ and the dependent variable is ____.

teaching methods; the social skills that are learned

Which of the following z-score values represents the location closest to the mean?

z = +0.50

You are instructed to subtract four points from each score, square the resulting value, and find the sum of the squared numbers. How would this set of instructions be expressed in summation notation?

Σ(X - 4)^2

For a population with µ = 80 and σ = 6, what is the z-score corresponding to X = 68?

​-2.00

For the following distribution of quiz scores, if a score of X = 3 or higher is needed for a passing grade, how many individuals passed?​ X f 5 6 4 5 3 5 2 3 1 2 ​

​16

A population has a sum of the squared deviation scores, SS = 100 and a variance, σ 2 = 4. How many scores are in the population?

​25

A sample of n = 25 scores has mean M = 20 and variance s2 = 9. What is the sample standard deviation?

​3

A sample of n = 6 scores has Σ X = 30. What is the sample mean?

​5

A population with a mean of µ = 6 has ΣX = 42. How many scores are in the population?

​N = 42/6 = 7

A recent study reports that elementary school students who were given a nutritious breakfast each morning had higher test scores than students who did not receive the breakfast. For this study, what is the independent variable?​

​Whether or not a breakfast was given to the students

For a particular sample of size n=10, the largest distance (deviation) between a score and the mean is 11 points. The smallest distance between a score and the mean is 4 points. Therefore, the standard deviation will be ____.

​between 4 and 11

A distribution is positively skewed. Which is the most probable order, from smallest to largest, for the three measures of central tendency?

​mode, median, mean

A population has µ = 50 and σ = 5. If 10 points are added to every score in the population, then what are the new values for the mean and standard deviation?

​µ = 60 and σ = 5

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