Exam 7: Inference for Means

A one-sample t test of H₀:  = 125 against H_a:  > 125 is carried out based on sample data from a Normal population.The SRS of size n = 15 produced a mean of = 132.8 and s = 12.6.What is the P-value of the test in this situation?

Assume that sample data,based on two independent samples of size 25,give us = 505, = 515,s₁ = 23,and s₂ = 28.What is a 95% confidence interval (use the conservative value for the degrees of freedom)for ₂ - ₁?

A study was done to determine if students learn better in an online basic statistics class versus a traditional face-to-face (f2f)course.A random sample of 12 students in an online course and 15 students in an f2f course was taken.The scores (out of 100)on the final exam of both groups are shown below. The standard error for the mean of the f2f group is ____.

A study was done to determine if students learn better in an online basic statistics class versus a traditional face-to-face (f2f)course.A random sample of 12 students in an online course and 15 students in an f2f course was taken.The scores (out of 100)on the final exam of both groups are shown below. The standard error for the mean of the online group is _____.

Sixteen people volunteered to be part of an experiment.All 16 people were Caucasian,between the ages of 25 and 35,and supplied with nice clothes.Eight of the people were men and eight were women.The question of interest in this experiment was whether females received faster service at restaurants than males.Each of the eight male participants was randomly assigned a restaurant,and each of the eight female were randomly assigned to one of these same eight restaurants.One Friday night,all 16 people went out to eat,each one alone.The men and women assigned to the same restaurant arrived within 5 min of each other,with the order determined by flipping a coin (man first or woman first).Each person then ordered a similar drink and a similar meal.The times (in minutes)until the food arrived at the table was recorded.They are shown below. The hypotheses being tested are H₀:  = 0 versus H_a:  > 0,where  represents the mean of the differences in service time (men - women).Assume that the differences are Normally distributed.What can you say about the value of the P-value?

The standard deviation of a statistic is known as the ________.

We wish to see if the electronic control indicating the oven temperature for a certain model oven is properly calibrated.Four ovens of this model are selected at random.The electronic control on each is set to 300°F;after 1 hour,the actual temperature of each is measured.The temperatures measured are 305°F,310°F,300°F,and 305°F.Assume that the distribution of the actual temperatures for this model when the electronic control is set to 300°F is Normal.To test if the electronic control is properly calibrated,we will test the following hypotheses: H₀:  = 300 versus H_a:   300.Based on the data,what is the value of the one-sample t statistic?

Robustness refers to how sensitive probability calculations are when assumptions are not met.

Bags of a certain brand of tortilla chips claim to have a net weight of 14 ounces.Net weights actually vary slightly from bag to bag.Assume net weights are Normally distributed.A representative of a consumer advocate group wishes to see if there is any evidence that the mean net weight is less than advertised and so intends to test the hypotheses H₀:  = 14 versus H_a:  < 14.To do this,he selects 16 bags of tortilla chips of this brand at random and determines the net weight of each.He finds a sample mean of 13.88 ounces with a standard deviation of s = 0.24 ounces.What is the value of the test statistic?

What assumption is necessary in order to perform a t procedure?

A study was conducted to determine if taking a popularly advertised herbal supplement will result in weight loss in obese males.A random sample of clinically obese males was obtained.Each subject was weighed before taking the supplement and again after 60 days using the supplement.Subjects were told not to alter their diet in any way during the study period.The following table shows the observed results for the six subjects. With  = 0.05,what observed values of the test statistic would cause the sample results to be declared statistically significant?

If the data are not normal and you wish to use a t procedure,one option is to __________.

A study was done to determine whether there is a difference in the amount of time (in hours)that graduate students versus undergraduate students spend on the Internet per day.The results of the analysis are shown below. To lower the P-value,you could ______.

You are interested in determining if the average amount of time (in hours)that students spend on the Internet per day is greater than 2 hours.The data below are from a random sample of 11 students. What is the value of the sample mean after removing the second observation (value = 100)?

A study was done to determine whether there is a difference in the amount of time (in hours)that graduate students versus undergraduate students spend on the Internet per day.The results of the analysis are shown below. What type of t procedure was used for this test?

Sixteen people volunteered to be part of an experiment.All 16 people were Caucasian,between the ages of 25 and 35,and supplied with nice clothes.Eight of the people were men and eight were women.The question of interest in this experiment was whether females received faster service at restaurants than males.Each of the eight male participants was randomly assigned a restaurant,and each of the eight female were randomly assigned to one of these same eight restaurants.One Friday night,all 16 people went out to eat,each one alone.The men and women assigned to the same restaurant arrived within 5 min of each other,with the order determined by flipping a coin (man first or woman first).Each person then ordered a similar drink and a similar meal.The times (in minutes)until the food arrived at the table was recorded.They are shown below. The hypotheses being tested are H₀:  = 0 versus H_a:  > 0,where  represents the mean of the differences in service time (men - women).Assume that the differences are Normally distributed.What is the value of the t test statistic?

A simple random sample of five basketball players is selected.Their heights (in centimeters)are 170,175,169,183,and 177.What is the standard error of the mean of these height measurements?

A study was done to determine if students learn better in an online basic statistics class versus a traditional face-to-face (f2f)course.A random sample of 12 students in an online course and 15 students in an f2f course was taken.The scores (out of 100)on the final exam of both groups are shown below. Using a significance level of  = .05,the null hypothesis would be rejected.

The sign test requires that the population distribution be ______.

Distribution-free procedures are often called _____.