Psych 311 Exam 2

A gambler rolls a 3 with one roll of a single fair die. Given that the die was six-sided, what was the probability of rolling a 3 with one roll?

1/6

The following are six random outcomes for a sample space: -1, -3, -3, -2, -5, and -6. What is the probability of selecting a -3 in this example?

2/6

The sample variance is an unbiased estimator of the population variance

when dividing SS by df, and when dividing SS by n-1

A researcher selects a sample of size 6 from a population of size 10. How many possible samples of this size can be selected using theoretical sampling?

1,000,000

Memorize

27

A researcher states that a sample of 100 shoppers spend 112 ± 40 (M ± SEM) dollars on groceries each week. Which value is the standard error of the mean?

40

The average sample variance equals the population variance when dividing SS by df.

true

The central limit theorem states that the sample mean will equal the population mean on average.

false

T/F A binomial probability distribution is the distribution of random outcomes for a bivariate or dichotomous random variable.

true

T/F For a set of data with 25±2.5, at least 95% of scores fall between 20 and 30.

true

T/F Probability distributions display the probability of each possible outcome for a given random variable.

true

T/F Probability ranges between 0 and 1 and is never negative.

true

T/F The expected value of a random variable is the mean of a probability distribution.

true

What is the z score for scores in the bottom 10%?

-1.28

Assume number of days absent is normally distributed. If a sample mean is 8 and SD is 2, what's the z-score for a person with 2 days absent?

-3

Suppose that the probability that any child of alcoholic parents becomes alcoholic is p = .16. Assuming independent outcomes, the probability that two children of alcoholic parents will be alcoholic equals

.03

A researcher selects a sample of 9 participants from a population with a mean of 8 and a standard deviation of 3. About 14% of the sample means in this sampling distribution should be between a sample mean of

9 and 10

T/F A binomial probability distribution is constructed for random variables that have at least two possible outcomes.

False

T/F While the expected value of the mean estimates the average outcome, the standard deviation of a probability distribution estimates the distance that all other outcomes deviate from the mean.

True

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

Which rule states that when two outcomes are mutually exclusive, the probability that either one of these outcomes will occur is the sum of their individual probabilities?

additive rule

Most behavior is believed to ________ a normal distribution.

approximate

As sample size increases, the standard error of the mean

decreases

The mean of a probability distribution is called the

expected value of the mean, and the mathematical expectation

In a normal distribution, 50% of all data:

fall above the mean, fall below the mean, and fall above and below the mode

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

T/F In a normal distribution a score of 8 will always be more probable than a score of 0.

false

T/F The probability of an outcome is particularly useful for predicting the likelihood of fixed events.

false

A theoretical distribution that evenly distributes data around the mean, median, and mode is called the

normal distribution, bell shaped distribution, and the Gaussian distribution

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 D

The proportion or fraction of times an outcome is likely to occur is referred to as

probability

The distribution of probabilities for each outcome of a random variable that sums to 1.00 is called a

probability distribution

A researcher selects from a participant pool of 4 males and 6 females. He determines that the probability of selecting 2 male participants is p = .16. Based on this probability, what strategy did the researcher use to sample participants.

sampling with replacement

Increasing the number of observations or samples in a study will decrease the standard error (standard error of the mean). This is known as

the law of large numbers

Each of the following is an example of a binomial distribution, except

the time it takes to complete a driving test

The following samples were selected by two researchers. Which is associated with a smaller standard error of the mean? Researcher A: n = 25, = 5, = 7 Researcher B: n = 25, = 32, = 7

they both have the standard error

Which of the following is not a step to locate a score in a normal distribution?

transform a raw score (x) into a z score

A researcher selects a sample of 625 participants from a population with a mean of 120 and a standard deviation of 25. The probability of selecting a sample mean that is larger than 125 is close to zero.

true

A researcher records the following data for the number of bids made on a sample of items sold at an auction. Based on the table, what was the probability that an item had 7 bids made on it? Number of Bids Frequencies 3 5 4 12 5 7 6 6 7 10

.25

The probability that someone in the human population has blood type AB is about p = .08; the probability that someone has blood type O is about p = .25. Knowing that each individual can have one and only one blood type, what is the probability that a person has an AB or O blood type?

.33

A professor records the grades for his class of students. He finds that the probability that a student earns an A is p = .14; earns a B is p = .36; earns a C is p = .32; earns a D is p = .10; and earns an F is p = .08. What is the probability that a student earns a B or better in this class?

.50

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

1/2

T/F The probability that a participant is married is p(M) = .60. The probability that a participant is married and "in love" is p(M∩L) = .46. Thus, the probability that a participant is in love, given that the participant is married is p = .77.

true

T/F The sample space is equal to the total number of random outcomes possible for a random variable.

true

The sample mean is an unbiased estimator of the population mean.

true

The sampling distribution of the mean has minimum variance.

true

The sampling distribution of the mean is a distribution of all the possible samples of a particular size that can be selected from a given population.

true

The standard error of the mean is the standard deviation in a sampling distribution of sample means.

true

There are 25 possible samples of size 2 that can be selected from a population of 5 people using theoretical sampling.

true

There are more possible samples that can be selected using theoretical sampling than using experimental sampling for any sample size greater than 1.

true