psyc 104 3

A research team believes that a recently discovered treatment will have an effect on the dependent variable. They randomly selects a sample of 12 people, and with their permission, provides them a treatment. They then evaluate the evidence regarding whether their treatment had an effect. Here's the data:The mean for their sample is 106. The mean for the population is 109, with a standard deviation of 16. Assume a normal distribution for the individual scores.The Z-test let's the reader know the number of standard errors between the sample mean and the population mean.Calculate and report the Z-test (Round to the nearest hundredth).

-0.65

Tiana randomly selects a sample of 13 people, and gives them a treatment. She then evaluates the evidence regarding whether her treatment had an effect. Here's the data:The mean for her sample is 88. The mean for the population is 95, with a standard deviation of 14. Assume a normal distribution for the individual scores.The Z-test tells the reader know the number of standard errors between the sample mean and the population mean.Calculate and report the Z-test (Round to the nearest hundredth).

-1.8

Mike believes that 12 units is no longer the 'typical load' at his college. His research hypothesis is therefore that the new average will either be more or less than 12 units. He randomly selects 49 students, and finds that their average number of units is 11 (with an estimated population standard deviation of 3.5). What is the t test statistic value for this problem?

-2

Joe randomly selects a sample of 16 people, and gives them a treatment. He then wants to evaluate the evidence regarding whether his treatment had an effect. Here's the data:The mean for his sample is 85. The mean for the population is 92, with a standard deviation of 13. Assume a normal distribution for the individual scores.The Z-test let's the reader know the number of standard errors between the sample mean and the population mean.Calculate and report the Z-test (Round to the nearest hundredth).

-2.15

Joe randomly selects a sample of 13 people, and gives them a treatment. He then wants to evaluate the evidence regarding whether his treatment had an effect. Here's the data:The mean for his sample is 93. The mean for the population is 105, with a standard deviation of 15. Assume a normal distribution for the individual scores.The Z-test let's the reader know the number of standard errors between the sample mean and the population mean.Calculate and report the Z-test (Round to the nearest hundredth).

-2.88

I set my alpha level to .05. Assuming that the null hypothesis is true, what is the probability of my retaining the null hypothesis?

.95

Kristy believes that caffeine affects impulse control. Before conducting her experiment, she sets her alpha level to .05. She then randomly selects 40 participants, who give their informed consent to participate. If the null hypothesis is true (i.e., no effect of caffeine on impulse control), what is the probability of Kristy making either a Type I Error or a Correct Decision? p(Type I Error) + p(Correct Decision) = ??

.95

Kristy believes that caffeine affects impulse control. Before conducting her experiment, she sets her alpha level to 0.01. She then randomly selects 40 participants, who give their informed consent to participate. If the null hypothesis is true (i.e., no effect of caffeine on impulse control), what is the probability of Kristy making a Type I Error?

.99

A research team believes that a recently discovered treatment will decrease scores. They randomly selects a sample of 18 people, and with their permission, provides them a treatment. They then evaluate the evidence regarding whether their treatment had an effect. Here's the data:The mean for their sample is 98. The mean for the population is 104, with a standard deviation of 18. Assume a normal distribution for the individual scores.The research team sets their alpha level to .05. .Calculate the Z test, and decide whether the research team should: 0 - Retain the null hypothesis 1 - Reject the null hypothesis.Provide as your answer the number (0 or 1) that corresponds to your decision:

0 (Z-test=-1.41)

A research team believes that a recently discovered treatment will have an effect on the dependent variable. They randomly selects a sample of 18 people, and with their permission, provides them a treatment. They then evaluate the evidence regarding whether their treatment had an effect. Here's the data:The mean for their sample is 95. The mean for the population is 92, with a standard deviation of 18. Assume a normal distribution for the individual scores.The research team sets their alpha level to .05. .Calculate the Z test, and decide whether the research team should: 0 - Retain the null hypothesis 1 - Reject the null hypothesis.Provide as your answer the number (0 or 1) that corresponds to your decision:

0 (Z-test=0.71)

A research team believes that a recently discovered treatment will have an effect on the dependent variable. They randomly selects a sample of 13 people, and with their permission, provides them a treatment. They then evaluate the evidence regarding whether their treatment had an effect. Here's the data:The mean for their sample is 103. The mean for the population is 91, with a standard deviation of 11. Assume a normal distribution for the individual scores.The research team sets their alpha level to .05. .Calculate the Z test, and decide whether the research team should: 0 - Retain the null hypothesis 1 - Reject the null hypothesis.Provide as your answer the number (0 or 1) that corresponds to your decision:

0 (Z-test=3.93)

Dr. Javon believes that his new aspirin, Xenorite, affects the severity of headaches. He recruits nine subjects who are experiencing a headache. He measures the initial severity of the person's headache, then gives them the new aspirin, and finally measures the severity of the headache again. His hypothesis is that Xenorite will affect the severity of the headache. The p-value for the t-test is......(round to the nearest thousandth; note that if Dr. Javon has a one-tail hypothesis, then divide the p-value in half before reporting here).

0.005

Joe sends out a survey asking several college students their college major. Later, he sends out another survey to ask another group of college students their sex (male or female). Assume that these two variables are independent of each other, and that the responses for each variable are mutually exclusive. Below are the frequency tables, showing his results for these questions. What is the probability of randomly selecting a college student at Washington who is both Male and a Business major? Round to the nearest hundredth.

0.13

Joe sends out a survey asking several college students their college major. Later, he sends out another survey to ask another group of college students their sex (male or female). Assume that these two variables are independent of each other, and that the responses for each variable are mutually exclusive. Below are the frequency tables, showing his results for these questions. What is the probability of randomly selecting a college student at Washington who either a Male or a Female? Round to the nearest hundredth.

1

Sally offers an workshop to improve student's g.p.a. The national average for g.p.a. is 2.17, with a standard deviation of 0.49. 20 students take Sally's workshop, and the next semester their average g.p.a. is 2.49. Assume a normal distribution for the individual scores. Should Sally reject the null hypothesis?If you think Sally should retain the null hypothesis, then type in the number zero as your answer. If you think she should reject the null hypothesis, then type in the number 1 as your answer.

1

A research team believes that a recently discovered treatment will decrease scores. They randomly selects a sample of 14 people, and with their permission, provides them a treatment. They then evaluate the evidence regarding whether their treatment had an effect. Here's the data:The mean for their sample is 99. The mean for the population is 105, with a standard deviation of 13. Assume a normal distribution for the individual scores.The research team sets their alpha level to .05. .Calculate the Z test, and decide whether the research team should: 0 - Retain the null hypothesis 1 - Reject the null hypothesis.Provide as your answer the number (0 or 1) that corresponds to your decision:

1 (Z-test=-1.73)

A research team believes that a recently discovered treatment will have an effect on the dependent variable. They randomly selects a sample of 17 people, and with their permission, provides them a treatment. They then evaluate the evidence regarding whether their treatment had an effect. Here's the data:The mean for their sample is 109. The mean for the population is 94, with a standard deviation of 18. Assume a normal distribution for the individual scores.The research team sets their alpha level to .05. .Calculate the Z test, and decide whether the research team should: 0 - Retain the null hypothesis 1 - Reject the null hypothesis.Provide as your answer the number (0 or 1) that corresponds to your decision:

1 (Z-test=3.44)

Tom believes that students at his college watch less TV than the national average of 20 hours a week. He randomly selects 36 students, and finds that their average TV watching time is 17 hours a week (with an estimated population standard deviation of 15). What is the t-critical value for this problem? Note that the t-critical value can be looked up in the t-table. Enter the entire t-critical value (do not round).

1.690

Jill is curious whether six year olds at her school are taller than 52 inches. She randomly selects 25 students, and finds that their average height is 54 inches (with a standard deviation of four inches). What is the t-critical value for this problem? Note that the t-critical value can be looked up in the t-table. Enter the entire t-critical value (do not round).

1.711

Susan is told that most college students work 15 hours a week. She thinks that this hypothesized population mean of 15 hours is incorrect. Instead, her research hypothesis is that students on average work more than 15 hours a week. Her null hypothesis is that students work 15 or fewer hours each week.Susan randomly samples 16 college students, and finds that the sample mean is 21 hours of work each week. Based upon the sample, the estimated population standard deviation is 12 hours. What is the t-critical value for this problem? Note that the t-critical value can be looked up in the t-table. Enter the entire t-critical value (do not round).

1.753

Susan is told that most college students work 15 hours a week. She thinks that this hypothesized population mean of 15 hours is incorrect. Instead, her research hypothesis is that students on average work more than 15 hours a week. Her null hypothesis is that students work 15 or fewer hours each week.Susan randomly samples 16 college students, and finds that the sample mean is 21 hours of work each week. Based upon the sample, the estimated population standard deviation is 12 hours. What is the degrees of freedom for this problem?

15

Susan is told that most college students work 15 hours a week. She thinks that this hypothesized population mean of 15 hours is incorrect. Instead, her research hypothesis is that students on average work more than 15 hours a week. Her null hypothesis is that students work 15 or fewer hours each week.Susan randomly samples 16 college students, and finds that the sample mean is 21 hours of work each week. Based upon the sample, the estimated population standard deviation is 12 hours. What is the t test statistic value for this problem?

2

You are curious whether there are an equal number of students with each type of eye color in your classroom. You have three categories: Hazel, Blue, and Brown. How many degrees of freedom are there in this problem?

2

Mike believes that 12 units is no longer the 'typical load' at his college. His research hypothesis is therefore that the new average will either be more or less than 12 units. He randomly selects 49 students, and finds that their average number of units is 11 (with an estimated population standard deviation of 3.5). What is the t-critical value for this problem? Note that the t-critical value can be looked up in the t-table. Enter the entire t-critical value (do not round).

2.014

Jill is curious whether six year olds at her school are taller than 52 inches. She randomly selects 25 students, and finds that their average height is 54 inches (with a standard deviation of four inches). What is the t test statistic value for this problem?

2.5

Jill is curious whether six year olds at her school are taller than 52 inches. She randomly selects 25 students, and finds that their average height is 54 inches (with a standard deviation of four inches). What is the degrees of freedom for this problem?

24

Tom believes that students at his college watch less TV than the national average of 20 hours a week. He randomly selects 36 students, and finds that their average TV watching time is 17 hours a week (with an estimated population standard deviation of 15). What is the degrees of freedom for this problem?

35

Assume that we have a normal distribution of scores, with a mean of 100 and a standard deviation of 16. We could expect the distribution of sample means to be smallest in the case where our sample size was 27, 36, 31, 18

36

Mike believes that 12 units is no longer the 'typical load' at his college. His research hypothesis is therefore that the new average will either be more or less than 12 units. He randomly selects 49 students, and finds that their average number of units is 11 (with an estimated population standard deviation of 3.5). What is the degrees of freedom for this problem?

48

Dr. Jones wishes to improve people's memory for names. On average, people can remember the names of 5 people to whom they have recently been introduced. The population standard deviation is 2.5. The shape of the distribution is normal. After a group of 9 people take Dr. Jone's course, they are able to remember on average 7 names of people to whom they are introduced. What is the sample mean in this problem?

7

You are told that an equal number of oranges, apples, and bananas were placed into a large fruit bin. All the fruit is mixed up in the bin. Looking more closely, you begin to wonder whether there actually is an equal amount of apples, oranges, and bananas in the bin. You take a random sample of 21 fruits. In your sample there are 3 apples, 13 oranges, and 5 bananas. Now you wish to reject the null hypothesis that there is an equal amount of apples, oranges, and bananas in the bin. What statistical test might you use?

Chi-Square Goodness of Fit

I am interested in whether there are more males or females attending college. I randomly select 100 college students, and find that 60 are female and that 40 are male. What type of inferential test will I use to evaluate the results?

Chi-Square Goodness of Fit Test

Dr. Javon believes that a new drug may affect (for better or worse) people's recovery from a local illness. He randomly selects 40 ill people from the local population, and randomly assigns them to two groups (0mg dose of medicine vs. 10mg dose of medicine). He then measures their level of symptoms to the illness. Note: When measuring illness, a value of zero indicates that the person is not ill (and there are equal intervals; the difference between 80 to 89, is the same as the difference from 90 to 99). The variability of the illness scores for the 0mg and the 10mg conditions indicates:

Equal variances can be assumed

John runs an experiment with an alpha of 0.05. He is able to reject the null. John then runs a second experiment with an alpha of .05. Assume that the null hypothesis was correct both times... What probability theorem would we use to calculate the probability of incorrectly rejecting the null hypothesis twice in a row?

Multiplication Theorem of Probability The multiplication theorem is: p(A and B) = p(A) * p(B).

With Alpha set to .05, what happens to the probability of a Type I Error, when we increase our sample size?

Nothing

Dr. Javon believes that his new aspirin, Xenorite, affects the severity of headaches. He recruits nine subjects who are experiencing a headache. He measures the initial severity of the person's headache, then gives them the new aspirin, and finally measures the severity of the headache again. His hypothesis is that Xenorite will affect the severity of the headache. Dr. Javon should analyze the data using a(n):

Paired Samples t Test

Yoshima believes that there is a correlation between height and SAT score. He randomly surveys 50 students. A preliminary analysis of the data reveals that the two scale variables are normally distributed. In looking at the scatterplot, the data is not curvi-linear. What statistical test should be used to analyze the data?

Pearson's r

You want to evaluate whether there is a relationship between Emotional IQ and Salary. Both variables are scale and normal. The relationship between the variables on the scatter plot appears fairly linear. Which test should you use?

Pearson's r

Doug believes that college students go to the movies more often than the general population. The population mean is 5 movies per year, with a population standard deviation of 2 movies. The distribution is positively skewed. Doug interviews a sample of 80 college students, and finds that the sample mean is 6 movies per year. What statistical test should be used to analyze the data?

Single Sample t Test

Dr. Javon believes that a new drug may affect (for better or worse) people's recovery from a local illness. He randomly selects 40 ill people from the local population, and randomly assigns them to two groups (0mg dose of medicine vs. 10mg dose of medicine). He then measures their level of symptoms to the illness. Note: When measuring illness, a value of zero indicates that the person is not ill (and there are equal intervals; the difference between 80 to 89, is the same as the difference from 90 to 99). Dr. Javon should analyze the data using a(n):

Single Sample t Test - The data is scale - There are two groups - It is hoped that there will be a difference between the two condition

Fukuko believes that people who read more attend movies less often. She surveys twenty-five college students. She records her results using two ordinal variables. "How often do you go to the movies each year? 1 - Less than three times; 2 - Between three & five times; 3 - More than five times.How many books do you read for pleasure each year? 1 - Less than three books; 2 - Between three & five books; 3 - More than five books."An initial analysis of the scatterplot reveals that the data is not curvilinear. What statistical test should she use to analyze her data?

Spearman's rho

Kristy believes that caffeine affects impulse control. Before conducting her experiment, she sets her alpha level to .05. She then randomly selects 40 participants, who give their informed consent to participate. If the null hypothesis is false, what is the probability of Kristy correctly rejecting the null hypothesis?

That would depend upon the size of her sample, how strongly caffeine effects impulse control, how she operationally defined caffeine (e.g., size of the dosage), etc.

Imagine that alpha is .05, and that our hypothesis is two-tailed. We place .025 alpha on the end of the left side of the null distribution, and we place another .025 alpha on the end of the right side of the null distribution. Our overall alpha is 0.025 + 0.025 = 0.05. We can do this because...

The .025 alpha on the end of the left side of the null distribution and the .025 alpha on the end of the right side of the null distribution are mutually exclusive

In hypothesis testing, what are we measuring the probability of?

The probability that if the null hypothesis was true, that we could get the results due to chance (i.e., random selection)

Dr. Jones wishes to improve people's memory for names. On average, people can remember the names of 5 people to whom they have recently been introduced. The population standard deviation is 2.5. The shape of the distribution is normal. After a group of 9 people take Dr. Jone's course, they are able to remember on average 7 names of people to whom they are introduced. We should reject the null hypothesis (and support the research hypothesis).

True

Sally's research hypothesis is that kissing on the first date is related to the length of a romantic relationship. She interviews 100 people about the length of their most recently ended romantic relationship... asking whether they had kissed on the first date and the length of the relationship. Her data supports her research hypothesis.How small must the probability of her results occurring due to sampling error be... before she can say that she 'proved' her research hypothesis?

With inferential statistics, you can never say that you proved your research hypothesis.

Joe is interested in whether the SAT scores of students at his college is greater than the national average. The national average SAT score is 800, with a population standard deviation of 200. The population of SAT scores is normally distributed. Joe samples 100 students at his college, and finds the sample mean to be 1100. What statistical test should Joe use to analyze the data?

Z test

Raleigh is interested in whether the IQ scores of students at his college are greater than the national average. The national average IQ score is 100, with a population standard deviation of 100. The population of IQ scores is normally distributed. Raleigh samples 50 students at his college, and finds the sample mean to be 115. What statistical test should Raleigh use to analyze the data?

Z test

Tim believes that the income of students at his college is less than the national average. The national average is $12,000, with a population standard deviation of $5,300. Note that the distribution is negatively skewed. Tim randomly samples 1,000 college students. The sample mean is $7,400. What statistical test should Tim use to analyze his data?

Z test

If the research hypothesis is true, we expect the ____________ variability to be larger than the ____________ variability.

between group; within group

Kristy believes that caffeine affects impulse control. Before conducting her experiment, she sets her alpha level to .05. She then randomly selects 40 participants, who give their informed consent to participate. If the null hypothesis is true (i.e., no effect of caffeine on impulse control).... Then the probability of Kristy making either a Type I Error or a Type II Error equals one.

false

If we retain the null hypothesis, when the null hypothesis is false, we have:

made a Type II error

Tom believes that students at his college watch less TV than the national average of 20 hours a week. He randomly selects 36 students, and finds that their average TV watching time is 17 hours a week (with an estimated population standard deviation of 15). Should we reject the null hypothesis?

no

Dr. Javon believes that his new aspirin, Xenorite, affects the severity of headaches. He recruits nine subjects who are experiencing a headache. He measures the initial severity of the person's headache, then gives them the new aspirin, and finally measures the severity of the headache again. His hypothesis is that Xenorite will affect the severity of the headache. The distribution of 'Before Aspirin' scores is considered

normal

Your friend believes that drinking tomato juice each morning helps to improve his college g.p.a. He goes out and randomly selected 25 college-bound students, and has them drink tomato juice during their entire time in college. Next, he compares the g.p.a. for his sample (of 25 students) to the entire college population.When it it time to do the hypothesis test, he sets his alpha to .05. Assume that tomato juice has nothing to do with g.p.a. (i.e., that the null hypothesis is true)..... What is the probability that his sample of 25 college students' g.p.a. will be high enough that he will erroneously reject the null hypothesis?

not .95 Just due to chance, our friend might have randomly selected students that were brighter and/or more motivated than the typical college student. All inferential statistics are based upon probability, distribution of sample means, and hypothesis testing. With inferential statistics, we can set the level at which we are willing to incorrectly reject the null hypothesis (alpha level). This level is typical set to .05. While we could further reduce the probability of incorrectly rejecting the null hypothesis (e.g., setting alpha to .01), this would make it harder for us to support a real effect (its a trade off).

Joe's research hypothesis is a prediction that can never be shown to be wrong. Joe says that all people commit every single detail of their life perfectly to memory, but that sometimes we can't recall the event. But consider that sometimes you may later recall what happened. Joe's hypothesis is:

not falsifiable

Doug believes that eating pickles decreases how long a person can stay up without feeling the need for sleep. He randomly selects forty people, who kindly provide their informed consent to participate. Doug gives everyone in his treatment group 8 oz of pickels with their lunch. The average amount of sleep the treatment group had averaged 7.2 hours a night. The population mean is 8 hours, with a standard deviation of 1.5 hours. This is an example of a _______________-tail hypothesis.

one

Yvonne believes that amount of time people spend in the sunlight each day is negatively correlated to level of mental health. This is an example of a ______ tail hypothesis.

one

Jill is curious whether six year olds at her school are taller than 52 inches. She randomly selects 25 students, and finds that their average height is 54 inches (with a standard deviation of four inches). Jill's research hypothesis is:

one-tail (directional)

Susan is told that most college students work 15 hours a week. She thinks that this hypothesized population mean of 15 hours is incorrect. Instead, her research hypothesis is that students on average work more than 15 hours a week. Her null hypothesis is that students work 15 or fewer hours each week.Susan randomly samples 16 college students, and finds that the sample mean is 21 hours of work each week. Based upon the sample, the estimated population standard deviation is 12 hours. Susan's research hypothesis is: Group of answer choices

one-tail (directional)

Tom believes that students at his college watch less TV than the national average of 20 hours a week. He randomly selects 36 students, and finds that their average TV watching time is 17 hours a week (with an estimated population standard deviation of 15). Tom's research hypothesis is:

one-tail (directional)

Dr. Javon believes that a new drug may affect (for better or worse) people's recovery from a local illness. He randomly selects 40 ill people from the local population, and randomly assigns them to two groups (0mg dose of medicine vs. 10mg dose of medicine). He then measures their level of symptoms to the illness. Note: When measuring illness, a value of zero indicates that the person is not ill (and there are equal intervals; the difference between 80 to 89, is the same as the difference from 90 to 99). The scale of measurement for the variable 'Illness' is:

ratio

Type I Error

rejecting a null hypothesis

The ___________ hypothesis is what the researcher expects to happen (either a difference or a relationship).

research

Type II Error

retaining the null hypothesis

Viviana read that preschoolers watch 21 hours of TV each week. She believes that the preschoolers at her school watch less TV than the national average. She also learns that the national distribution for preschoolers watching TV is negatively skewed, and that the population standard deviation is 5 hours. Viviana sends a survey home to the parents of 120 preschool children at her school. She discovers that the sample mean for her school is 19 hours. What statistical test should be used to analyze the data?

single sample t test We are comparing a single sample mean to a known or hypothesized population mean

Dr. Javon believes that his new aspirin, Xenorite, affects the severity of headaches. He recruits nine subjects who are experiencing a headache. He measures the initial severity of the person's headache, then gives them the new aspirin, and finally measures the severity of the headache again. His hypothesis is that Xenorite will affect the severity of the headache. Based on the SPSS analysis of data, the results should be written as follows: The decrease in severity of headaches (mean difference = -11) was

statistically significant, t(8) = -3.798, p ≤ .05.

Dr. Javon believes that a new drug may affect (for better or worse) people's recovery from a local illness. He randomly selects 40 ill people from the local population, and randomly assigns them to two groups (0mg dose of medicine vs. 10mg dose of medicine). He then measures their level of symptoms to the illness. Note: When measuring illness, a value of zero indicates that the person is not ill (and there are equal intervals; the difference between 80 to 89, is the same as the difference from 90 to 99). We would finish writing up the results (using APA style) as:People given a 10 mg dose reported a lower level of illness (M = 86. 8) than the group given 0 mg dose (M = 101.3). This difference was

t(38) = 5.63, p ≤ .05 The "t(38)"tells us that this a t Test, with thirty-eight degrees of freedom.

Joe believes that studying affects grades. The null hypothesis is that studying does not affect grades. If the null hypothesis is false, what is the probability that we will reject it?

that is unknown... it depends upon how helpful the studying was, and the size of the sample

1 - alpha level

the probability of rejecting the null hypothesis

Alpha level

the probability of retaining the null hypothesis

Doug believes that eating pickles affects how long a person can stay up without feeling the need for sleep. He randomly selects forty people, who kindly provide their informed consent to participate. Doug gives everyone in his treatment group 8 oz of pickels with their lunch. The average amount of sleep the treatment group had averaged 7.2 hours a night. The population mean is 8 hours, with a standard deviation of 1.5 hours. This is an example of a _______________-tail hypothesis.

two

Yvonne believes that amount of time people spend in the sunlight each day is related to level of mental health. This is an example of a ______ tail hypothesis.

two

Dr. Javon believes that a new drug may affect (for better or worse) people's recovery from a local illness. He randomly selects 40 ill people from the local population, and randomly assigns them to two groups (0mg dose of medicine vs. 10mg dose of medicine). He then measures their level of symptoms to the illness. Note: When measuring illness, a value of zero indicates that the person is not ill (and there are equal intervals; the difference between 80 to 89, is the same as the difference from 90 to 99). The type of hypothesis test that Dr. Javon will be using is a:

two-tail hypothesis test

Dr. Javon believes that his new aspirin, Xenorite, affects the severity of headaches. He recruits nine subjects who are experiencing a headache. He measures the initial severity of the person's headache, then gives them the new aspirin, and finally measures the severity of the headache again. His hypothesis is that Xenorite will affect the severity of the headache. The type of hypothesis test that Dr. Javon will be using is a:

two-tail hypothesis test (non-directional), because Dr. Javon believes that the new aspirin, Xenorite, will affect headaches - it could make it worse or better. It would have been one-tailed if Dr. Javon felt that the aspirin might decrease the severity of headaches (i.e., a directional hypothesis).

Dr. Jones wishes to improve people's memory for names. On average, people can remember the names of 5 people to whom they have recently been introduced. The population standard deviation is 2.5. The shape of the distribution is normal. After a group of 9 people take Dr. Jone's course, they are able to remember on average 7 names of people to whom they are introduced. What is the standard error in this problem? Round to the thousandths place.

use the Z-test

Jill is curious whether six year olds at her school are taller than 52 inches. She randomly selects 25 students, and finds that their average height is 54 inches (with a standard deviation of four inches). Should we reject the null hypothesis? Note that this is a single sample t-test.

yes

Susan is told that most college students work 15 hours a week. She thinks that this hypothesized population mean of 15 hours is incorrect. Instead, her research hypothesis is that students on average work more than 15 hours a week. Her null hypothesis is that students work 15 or fewer hours each week.Susan randomly samples 16 college students, and finds that the sample mean is 21 hours of work each week. Based upon the sample, the estimated population standard deviation is 12 hours. Should we reject the null hypothesis?

yes

Tanya believes that the number of units students at her college take is more than the national average. The national average is 12 units, with a population standard deviation of 3 units. Note that the distribution is negatively skewed. Tanya randomly samples 1,000 college students. The sample mean is 14.2 units. What statistical test should Tanya use to analyze her data?

z test