Psychology 211: Exam 2

What is the z score for a 5% level on a one-tailed test?

+1.64 and -1.64

What is the z score for a 5% level on a two-tailed test?

+1.96 and -1.96

•A team of researcher predict that showing a certain film will change people's attitudes toward alcohol. The researchers then randomly select 36 people, show them the film, and give them an attitude questionnaire. The mean score on the attitude test for these 36 people is 70. The score for people in general on this test is 75, with a standard deviation of 12. Using the five steps of hypothesis testing and the 5% significance level, carry out a Z test to see if viewing the film changes people's attitudes toward alcohol. What is/are the cutoff sample score(s)? •1.96 •1.64 •+1.96 and -1.96 •+1.64 and -1.64

+1.96 and -1.96

•A team of researcher predict that showing a certain film will change people's attitudes toward alcohol. The researchers then randomly select 36 people, show them the film, and give them an attitude questionnaire. The mean score on the attitude test for these 36 people is 70. The score for people in general on this test is 75, with a standard deviation of 12. Using the five steps of hypothesis testing and the 5% significance level, carry out a Z test to see if viewing the film changes people's attitudes toward alcohol. What is the sample's Z score? •2.5 •-2.5 •-1.25 •1.25

-2.5

The criterion or level of significance in behavioral research is typically set at what probability value (α)?

.05

What are the steps of the Hypothesis Testing Process?

1. Restate the question as a research hypothesis and a null hypothesis about the populations 2. Determine the characteristics of the comparison distribution 3. Determine the cutoff sample score on the comparison distribution at which the null hypothesis should be rejected 4. Determine your sample's score on the comparison distribution 5. Decide whether to reject the null hypothesis

What are the three characteristics of a distribution of means?

1. its mean 2. its spread (that is measured using the variance and standard deviation) 3. its shape

What are the rules of finding the characteristics of a distribution of means?

1. the mean of a distribution of means is the same as the mean of the population of individuals 2A. the variance of a distribution of means is the variance of the population of individuals divided by the number of individuals in each sample 2B. The standard deviation of a distribution of means is the square root of the variance of the distribution of means 3. The shape of a distribution of means is approximately normal if either each same is of 30 or more individuals or the distribution of the population is normal

what are the things to note about the of the characteristics of a distribution of means?

1. the mean of the distribution is about the same as the mean of the original population of individuals, which is true for all distributions of means 2. the spread of the distribution of means is less than the spread of the distribution of the population of individuals, which is true for all distributions of means 3. the shape of the distribution of means is approximately normal, which is true for most distributions of means

•A team of researcher predict that showing a certain film will change people's attitudes toward alcohol. The researchers then randomly select 36 people, show them the film, and give them an attitude questionnaire. The mean score on the attitude test for these 36 people is 70. The score for people in general on this test is 75, with a standard deviation of 12. Using the five steps of hypothesis testing and the 5% significance level, carry out a Z test to see if viewing the film changes people's attitudes toward alcohol. What is the standard deviation of the distribution of means? •14 •16 •4 •2

2

A population of scores has µ = 44. My sample has a mean of 40 which corresponds to z = -1.00. What is the standard deviation of the distribution of means? •4 •2 •-2 -4

4

The variance of the population of individuals is 400 and there are 25 individuals in each sample. What is the standard error of the mean? •16 •8 •4 •3.34

4

•A team of researchers predict that showing a certain film will change people's attitudes toward alcohol. The researchers then randomly select 36 people, show them the film, and give them an attitude questionnaire. The mean score on the attitude test for these 36 people is 70. The score for people in general on this test is 75, with a standard deviation of 12. Using the five steps of hypothesis testing and the 5% significance level, carry out a Z test to see if viewing the film changes people's attitudes toward alcohol. What is the variance of the distribution of means? •36 •4 •2 •14

4

How often will you make a Type 1 error if you set the significance level cut-off at .05?

5% of the time

What is a distribution of means? •A distribution of means of samples of a given size from a population. •The probability of a particular value or value range of a variable. •The mean of a distribution of means of samples of a given size from a population. •A distribution of individual scores taken from a population of individuals.

A distribution of means of samples of a given size from a population.

Which of the following is not a step in hypothesis testing? A) State the hypotheses B) Set the criteria for a decision C) Compute the test statistic D) Determine your theory

D

As sample size increases, the standard error of the mean... •Increases •Decreases •Can increase or decrease Stays the same

Decreases

•A team of researcher predict that showing a certain film will change people's attitudes toward alcohol. The researchers then randomly select 36 people, show them the film, and give them an attitude questionnaire. The mean score on the attitude test for these 36 people is 70. The score for people in general on this test is 75, with a standard deviation of 12. Using the five steps of hypothesis testing and the 5% significance level, carry out a Z test to see if viewing the film changes people's attitudes toward alcohol. Decide whether to reject the null hypothesis: •Reject the null hypothesis •Accept the null hypothesis

Reject the null hypothesis

•Several students took a standardized test to get into graduate school. The mean score for these students was 1000 and the standard deviation was 200. Arya made a score of 1200. What would her z-score be?

Z=+1 standard deviation above average

What is a power table?

a computer software to determine power

What is effect size?

a measure of the difference between population means

What is the symbol used for the significance level?

alpha

what is the symbol used for type 2 errors?

beta

what is type 2 error?

false negative

What is type 1 error?

false postivie

What determines the power of a study?

how big an effect (the effect size) the research hypothesis predicts and how many participants are in the study (the sample size)

•In a planned study, there is a know population with a normal distribution, μ = 0, and σ = 20. What is the predicted effect size if the researchers predict that those given an experimental treatment have a mean of 10? • •Small (.1,.2,.3) • •medium • •Large(.7,.8,1)

medium

The decision in hypothesis testing is to retain or reject which hypothesis: the null or alternative hypothesis?

null hypothesis

What does N stand for?

number of individuals in each sample

What is directional hypothesis?

predicting a particular direction of differences between populations

what is statistical power?

probability that the study will produce a statistically significant result if the research hypothesis is true

A researcher conducts a hypothesis test to evaluate the effect of a treatment. The hypothesis test produces a z-statistic of z = -2.60. Assuming that the researcher is using a two-tailed test, what is the correct statistical decision (Hint: use Table)? •reject the null hypothesis with either α = .05 or α = .01 •reject the null hypothesis with α = .05 but not with α = .01 •fail to reject the null hypothesis with either α = .05 or α = .01 •cannot answer without additional information

reject the null hypothesis with either α = .05 or α = .01

What are decision errors?

situations in which the right procedure lead to the wrong decisions

What does σM stand for?

standard deviation of the distribution of means

•A researcher computes a one-sample z-test in two studies. Both studies used the same alpha level, placed the rejection region in both tails, and measured the same sample mean. The researcher selects a sample of 30 participants in Study 1 and decides to retain the null hypothesis. She selects a sample of 60 participants in Study 2 and decides to reject the null hypothesis. Which of the following is the best explanation for why the decision was different in Study 1 and Study 2? •the different decisions in Study 1 and Study 2 are possible because the second test was associated with greater power to detect an effect •the different decisions in Study 1 and Study 2 are not possible because all values were the same •the different decisions in Study 1 and Study 2 are not possible because the researcher tested the same hypothesis •the different decisions in Study 1 and Study 2 are due to an error the researcher made in the first hypothesis test

the different decisions in Study 1 and Study 2 are possible because the second test was associated with greater power to detect an effect

When combining the results through meta-analysis, what do you get?

the effect sizes

the bigger the effect size...

the greater the power is

What is the general principle of what determines the power of a study through effect size?

the less overlap between the 2 distributions, the more likely it is that a study will give a significant result

What does μM stand for?

the mean of the distribution of means

What score do we care about the most?

the mean of the group of scores

What does μ stand for?

the mean of the population of individuals

What is meta-analysis?

the procedure that combines the results from multiple studies, even studies using different methods of measurement

A researcher expects a treatment to produce an increase in the population mean. The treatment is evaluated using a one tailed hypothesis test, and the test produces z = 1.85. Based on this result, what is the correct statistical decision? •the researcher should reject the null hypothesis with α = .05 but not with α = .01 •the researcher should reject the null hypothesis with either α = .05 or α = .01 •the researcher should fail to reject the null hypothesis with either α = .05 or α = .01 •cannot answer the question without additional information

the researcher should reject the null hypothesis with α = .05 but not with α = .01

What also effects power?

the significance level chosen, whether a 1 or 2 tailed test is used, and the kind of hypothesis-testing procedure

What is another name for the standard deviation of the distribution of means?

the standard error of the mean or the standard error

What is a one-tailed test?

the test of directional hypotheses and can be a test in either direction

What is a two-tailed test?

the test of non directional hypotheses and the sample could be extreme at either tail of the comparison distribution

what does calculating power when planning a study help you do?

to decide how many participants you need

What does σ2M stand for?

variance of the distribution of means

What does σ2 stand for?

variance of the population of individuals

What is a nondirectional hypothesis?

when a research hypothesis predicts an effect but does not predict the direction for the effect

If the null hypothesis is rejected, then did we reach significance?

yes

•Define​ 0.05 significance​ level •A 0.05 significance level is the cutoff on the comparison distribution with a probability of​ 95% that a score will be at least that extreme if the null hypothesis were true. This probability is usually written as p < 0.95. •A 0.05 significance level is the cutoff on the comparison distribution with a probability of​ 5% that a score will be at least that extreme if the null hypothesis were true. This probability is usually written as p < 0.05. • •A 0.05 significance level is the cutoff on the comparison distribution with a probability of​ 0.05% that a score will be at least that extreme if the null hypothesis were true. This probability is usually written as p < 0.0005. •A 0.05 significance level is the cutoff on the comparison distribution with a probability of​ 5% that a score will be at most that extreme if the null hypothesis were true. This probability is usually written as p > 0.05.

•A 0.05 significance level is the cutoff on the comparison distribution with a probability of​ 5% that a score will be at least that extreme if the null hypothesis were true. This probability is usually written as p < 0.05.

The following samples were selected by two researchers. Which is associated with a smaller standard error of the mean? •Researcher B •Researcher A •They both have the same standard error •There is not enough information to answer the question

•Researcher B

•Under what conditions is it reasonable to assume that a distribution of means will follow a normal​ curve? • •The distribution of means will follow a normal curve when the distribution of the population of individuals follows a normal​ curve, or when each sample is of 30 or more individuals. • •The distribution of means will follow a normal curve when the distribution of the population of individuals follows a normal​ curve, or when the variance of the distribution of the population of individuals is less than​ 20% of the mean. • •The distribution of means will follow a normal curve when the distribution of the population of individuals follows a normal curve and each sample is of 30 or more individuals. • •The distribution of means will always follow a normal curve.

•The distribution of means will follow a normal curve when the distribution of the population of individuals follows a normal​ curve, or when each sample is of 30 or more individuals.

What term is used to identify the standard deviation of the distribution of means? •The standard error of the mean (standard deviation of the distribution of means) •The expected value of the mean •The sample mean The central limit mean

•The standard error of the mean (standard deviation of the distribution of means)