PSY 2330 Exam 2

Which of the following are requirements of a random sample?

--every individual has an equal chance to be selected --the probabilities cannot change during a series of selections --there must be a sampling replacement

For a population with µ = 40 and σ = 8, what is the z‑score corresponding to X = 46?

0.75

For a sample with M = 60, which of the following values for the sample standard deviation would cause X = 68 to have the most extreme position in the distribution?

1

A jar contains 10 red marbles and 30 blue marbles. A random sample of n = 3 marbles is selected from the jar. If the first two marbles are both blue, what is the probability that the third marble will be red?

10/40

A jar contains 10 red marbles and 30 blue marbles. What is the probability of randomly selecting a red marble from the jar?

10/40

A sample of n = 100 scores was selected from a population with a µ = 100 and σ = 10. A sample has a mean of M = 102. What is the z-score corresponding to this sample mean?

2/1=2.00

What is the value of SS for the following set of scores? Scores: 8, 3, 1

26

X f 5 2 4 1 3 3 2 2 1 2 What is the mean for this distribution?

29/10 = 2.90

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

3

What is the median for the population of scores shown in the frequency distribution table? X f 5 2 4 2 3 3 2 4 1 2

3

For a perfectly symmetrical distribution with a median of 30, what is the value of the mean?

30

A sample of n = 4 scores was selected from a population with a µ = 100 and σ = 10. This sample has a mean of M = 95. What is the z-score corresponding to this sample mean?

5/5=-1

Samples of size n = 9 are selected from a population with μ = 60 with σ = 18. What is the expected value for the distribution of sample means?

60

What is the mean for the following sample of scores? Scores: 1, 4, 5, 10

Add up all the numbers and divde by the number of numbers. 20/4 = 5

A positive standard deviation indicates a score that is less than the mean.

False

What happens to the standard error of M as sample size increases?

It decreases.

In a population of N = 6, five of the individuals all have scores that are exactly 1 point above the mean. From this information, what can you determine about the score for the sixth individual?

It is below the mean by 5 points.

What happens to the expected value of M as sample size increases?

It stays constant = The expected value is always equal to the population mean.

Last week Sarah had exams in Math and in Spanish. On the Math exam, the mean was µ = 30 with σ = 5, and Sarah had a score of X = 45. On the Spanish exam, the mean was µ = 60 with σ = 8 and Sarah had a score of X = 68. In which class did Sara perform better relative to the other students in that class?

Math

A random sample of n = 4 scores is selected from a population. Which of the following distributions definitely will be normal?

Neither the sample, the population, nor the distribution of sample means will definitely be normal.

To examine the development of language skills from age 2 to 6, a developmental psychologist obtains three different groups of children, one for three different ages (2, 4, and 6), with 16 children in each of the three groups. Each child is given a language-skills assessment test. What type of study is this?

Quasi-experimental design

What are the values for SS and variance for the following sample of n = 3 scores? Sample: 1, 4, 7

SS = 18 and variance = 9

The value for SS is always greater than or equal to zero.

True

What term is used to identify the standard deviation of the distribution of sample means?

What term is used to identify the standard deviation of the distribution of sample means?

Which combination of factors will produce the smallest value for the standard error?

a large sample and a small standard deviation

A sample is obtained from a population with μ = 100 and σ = 20. Which of the following samples would produce the most extreme z-score?

a sample of n = 100 scores with M = 104

What position in the distribution corresponds to a z-score of z = 1.00?

above the mean by a distance equal to 1 standard deviation

Use this sample of scores to answer the following questions 1, 3, 5, 4, 7 Range = [d] Mean = [e] SS = [f] Variance = [g] Standard deviation = [h]

d: 7-1+1=7 e: 20/5=4 f:20 g: 20/n-1=5 h: sqr rt 5= 2.4

Questions that can be answered through systematic observation and data collection are called

empirical questions

To say that experience is the best teacher is to rely on __________ as a way of knowing.

empiricism

Your textbook authors discuss some reasons for taking a research methods course. Which of the following is NOT listed in the text as a reason for taking a research methods course?

it is the most important course in the psychology curriculum for achieving self-understanding

Compared to laboratory research, which of the following is true about field research?

it may be higher in mundane realism

A population of scores has a mean of µ = 26, a median of 23, and a mode of 22. What is the most likely shape for the population distribution?

positively skewed

Which of the following symbols identifies the sample standard deviation?

s

A set of 10 scores has SS = 90. If the scores are a sample, the sample variance is ____ and if the scores are a population, the population variance is ____.

s2 = 10; σ2 = 9

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

What term is used to identify the mean of the distribution of sample means?

the expected value of M

The smallest score in a population is X = 5 and the largest score is X = 10. Based on this information, you can conclude that

the population mean is between 5 and 10, and the standard deviation is less than 6.

The smallest score in a population is X = 5 and the largest score is X = 10. Based on this information, you can conclude that ______.

the population mean is between 5 and 10, and the standard deviation is less than 6.

A sample of n = 8 scores has a mean of M = 10. After one score is removed from the sample, the mean for the remaining score is found to be M = 11. What was the score that was removed?

the score was less than 10

All probabilities can be expressed as decimal values ranging from 0 to 1.00

true

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

true

A population distribution has σ = 6. What position in this distribution is identified by a z-score of z = +2.00?

twelve points above the mean

Use this population of scores to answer the following questions 1, 4, 6, 6, 9, 10 Mean = [w] SS = [x] Variance = [y] Standard deviation = [z]

w: 36/6 = 6 x: 54 y: 54/6 z:Sq rt 9 = 3

The distribution of sample means ____ .

we be normal if either the population is normal or the sample size is n > 30.

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

For a particular sample, the largest distance (deviation) between a score and the mean is 16 points. The smallest distance between a score and the mean is 2 points. Therefore, the standard deviation _____.

will be between 2 and 16

A sample of n = 9 scores is obtained from a population with μ = 70 and σ = 18. If the sample mean is M = 76, then what is the z-score for the sample mean?

z = 1.00

A sample of n = 20 scores has a mean of M = 45 and a standard deviation of s = 8. In this sample, what is the z-score corresponding to X = 57?

z = 1.50

Which of the following z-score values represents the location farthest away from the mean?

z=-2.00

You have a score of X = 65 on an exam. Which set of parameters would give you the best grade on the exam (compared to everyone else)?

μ = 60 and σ = 5

Which of the following symbols identifies the population variance?

σ 2

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

In a population of N = 10 scores, the smallest score is X = 8 and the largest score is X = 20. Using the concept of real limits, what is the range for this population?

13

Which set of scores has the smallest standard deviation? (Note: You don't have to compute standard deviation to answer this question.)

145, 143, 145, 147

If random samples, each with n = 4 scores, are selected from a normal population with µ = 80 and σ = 36, then what is the standard error for the distribution of sample means?

18

A sample of n = 100 scores is selected from a population with μ = 80 with σ = 20. On average, how much error is expected between the sample mean and the population mean?

2 pts - This question is asking for the standard error, which is how much error is expected between the sample mean and the population mean

A sample of n = 25 scores was selected from a population with a µ = 100 and σ = 10. A sample has a mean of M = 105. What is the z-score corresponding to this sample mean?

2.50

What symbol is used to identify the standard error of M?

σM