py 211 test 2

what are the cutoff z-score of one tailed tests at the 5% level

+/- 1.64

a team of researchers predict that showing a certain film will change people's attitude toward alcohol. the researchers then randomly selected 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

what are the cutoff z-score of two-tailed tests at the 5% level

+/-1.96

the criterion or level of significance in behavioral research is typically set at what probability value (x)

.05, .01

a population of scores has µ = 44. my sample of 40 which corresponds to z = -1.00. what is the standard deviation of the distribution of means

Z = M - µ (M) / SD µ(M) = µ so -1 = 40 - 44 / SD -1 = -10 / SD 4 = SD

what is a hypothesis

a prediction intended to be tested in a research study an if, then, because statement

the mean of the distribution of means is ______ the mean of the original population of individuals

about the same as

the shape of the distribution of means is....

approximately normal

a type 2 error is also called

beta

the bigger effect size, the _____ the power

bigger

the smaller standard deviation, the ______ effect size

bigger

what we use to make inferences from the data of our study/experiment used to determine how well the distribution can be approximated by the normal distribution

comparison distribution

population 2 in the muscle supplement example since this population represents the athletic performance if the null hypothesis is true

comparison distribution example

if what is measured/perceived is false and reality is false

correct

if what is measured/perceived is true and reality is also true

correct

if we accept null hypothesis (Ho) and the null hypothesis (Ho) is true

correct decision

if we reject null hypothesis (Ho) and alternative hypothesis (Ha) is true

correct decision

how extreme of a sample score would it have to be for it to be unlikely that they could get such an extreme score if the null hypothesis were true -probability of 5% -p < .05

cutoff sample score (critical value)

a team of researchers predict that showing a certain film will change people's attitude toward alcohol. the researchers then randomly selected 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

decide whether to reject the null hypothesis (Ho) 70 - 75 / 2 = -2.5 is -2.5 more extreme than -1.96? YES so REJECT the null hypothesis

as sample size (N) increases, the standard error of the mean...

decreases

using a more extreme significance level ___________ power

decreases

how does the following affect the power of a planned study? a larger population standard deviation _______ power and using a more extreme significance level (for example, 0.01 instead of 0.05) _______ power

decreases decreases

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

define 0.05 significance level

which of the following is not a step in hypothesis testing: state the hypothesis set the criteria for a decision compute the test statistics determine your theory

determine your theory

predicting a particular direction of differences between populations

directional hypothesis

predicting population 1 has a higher mean than population 2

directional hypothesis example

samples of a given size from a population

distribution of means

a measure of the difference between population means

effect size

a team of researchers predict that showing a certain film will change people's attitude toward alcohol. the researchers then randomly selected 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

find variance of distribution square root = 2

the bigger the mean difference, the ______ the power

greater

use table to find .05 or .01 in percentage in tail column

how to find percentages based on alpha

setting "a" to be low (i.e p < .001) can lead to a type 2 error

how to protect against type 1 errors

you can be more lenient significance level (p < 0.1) can lead to type 1 error

how to protect against type 2 error

a distribution of means will be ______ than the distribution of individuals from which the samples were taken

less spread out

the spread of the distribution of means is _____ the spread of the distribution of the population of indivduals

less than

in a planned study, there is a known 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

medium solve for affect size: d = (10 - 0) / 20 = 0.5

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

null hypothesis

the lack of difference between populations M1=M2

null hypothesis

there is no difference in the performance of athletes between population 1 and population 2 athletic performance is not influenced by whether athletes take the specially purified supplement

null hypothesis example

the test of a directional hypothesis can be a test in either direction (positive or negative)

one tailed test

a prediction about the difference between populations M1>M2

research hypothesis

population 1 athletes will on average perform better than population 2 athletes

research hypothesis example

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

solve for variance of distribution of means, square root it 400/25 = 16 square root of 16 = 4

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

statistical power

restate the question as a research hypothesis and a null hypothesis about the populations -state the research hypothesis -state the null hypothesis

step 1 of hypothesis testing

determine the characteristics of the comparison distribution -you compare the actual sample's score to the comparison distribution

step 2 of hypothesis testing

determine the cutoff sample score on the comparison distribution at which the null hypothesis should be rejected -ideally set a target against what they will compare your results to -they decide in advance that IF the result of their study is an athlete performing +2 standard deviations about the mean then they will reject the null hypothesis (Ho) -use cutoff score on comparison distribution with a probability of 5% that a score will be at least that extreme if the null hypothesis (Ho) is true -researchers REJECT the null hypothesis (Ho) is the probability of the sample score this extreme is less than 5%

step 3 of hypothesis testing

determine your sample's score on the comparison distribution -carry out experiment and get the results for sample -compute z-scores for the sample's raw score based on the population mean and standard deviation of comparison distribution

step 4 of hypothesis testing

decide whether to reject the null hypothesis (Ho) -compare your actual sample's z-score (step 4) to the cutoff z-score (step 3)

step 5 of hypothesis testing

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

if asked to find the standard error, what are you trying to find

the standard deviation of the distribution of means

term used to identify the standard deviation of the distribution of means

the standard error of the mean SE or SEM

a team of researchers predict that showing a certain film will change people's attitude toward alcohol. the researchers then randomly selected 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

two tailed solve for variance of distribution of means 12^2/36 = 144/36 = 4

research hypothesis states that an experimental procedure will have an effect, without saying it will produce a very high/low score

two tailed test (non directional hypothesis)

setting the significance level cutoff at 0.05 means that you will make a _____ error 5% of the time. the significance level (the chance of making this error) is called _______

type 1 alpha

if we reject the null hypothesis (Ho) but the null hypothesis (Ho) is true

type 1 error

if what is measured/perceived is true but reality is false

type 1 error (false positive)

if we accept null hypothesis (Ho) but the alternative hypothesis (Ha) is true

type 2 error

if what is measured/perceived is false and reality is true

type 2 error (false negative)

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

under what conditions is it reasonable to assume that a distribution of means will follow or normal curve

a researcher conducts a hypothesis test to evaluate the effect of a treatment. the hypothesis test procedures a z-statistic of z = -2.60. assuming that the researcher is using a two tailed test, what is the correct statistical decision

use z-table to find .05% in tail column should be 2.57 or 2.58 compare z-score to alpha values/is it more extreme

if the null hypothesis is rejected, then did we reach significance

yes

several students took a standardized test to get into grad school. the mean sore for these students was 1000 and the standard deviation was 200. Arya made a score of 1200. what would her z-score be?

z = 1200-200/1200 = +1