Stats Exam 3 Questions And Answers 100%
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An education specialist was studying SAT math scores at a local university. She found the
following 95% confidence interval for the population mean score for SAT math: (450, 550).
Suppose that a significance test at Ho:population mean = 475 versus Ha...
An education specialist was studying SAT math scores at a local university. She found the
following 95% confidence interval for the population mean score for SAT math: (450, 550).
Suppose that a significance test at Ho:population mean = 475 versus Ha: population mean does
not equal 475. The p-value for this test was 0.14. Which of the following statements accurately
describes this situation? - answer✔The population mean score for SAT Math is NOT statistically
or practically different from 475.
What is the definition of Type I error? - answer✔Rejecting the null hypothesis when the null
hypothesis is really true.
Should we focus on the p-value instead of the alpha level? - answer✔Yes - alpha is arbitrary,
while the p-value gives a better representation of the amount of evidence we have to reject the
null.
Now change the value of n and notice what happens to the Type I and II Errors. Which of the
following is the best description of the effect of increasing n? - answer✔Probability of Type I
Error does not change - that is given by alpha. But as the sample size n increases, the
Probability of a Type II Error decreases, making it easier to make a correct decision to Reject Ho.
A significance test is conducted to determine if the majority of students at UF have a paying job
at some time during the year.
Ho: p=0.5 vs Ha: p>0.5
What would a Type I Error mean in this setting? - answer✔Determining that it is more than half
of students in the population who have a job when in fact, it is really not.
When we make inferences about the difference of two independent population proportions,
what assumptions do we need to make? - answer✔Counts of successes and failures at least 15
each for each group.
Random samples.
Do less Republicans (group A) than Democrats (group B) favor the government investing billions
of dollars to improve the country's train system? One thousand Republicans and one thousand
Democrats were asked if they favored spending billions to improve the country's train system.
How would we write the alternative hypothesis? - answer✔Ha: pA - pB < 0
In 2012, the General Social Survey included a question that asked respondents if they had
"often/sometimes" been the subject of gossip at work. Out of 606 men, 75 said yes they had
"often/sometimes" been the subject of gossip at work. Out of 580 women, 67 said yes they had
"often/sometimes" been the subject of gossip at work. What is the pooled proportion for the
null hypothesis Ho:p1-p2=0 vs. alternative hypothesis Ha: p1-p2 does not equal 0? -
answer✔0.120
A social scientist is interested in determining if there is a significant difference in the proportion
of Republicans between two areas of town. He takes independent random samples of 200
families in each area of town and a significance test was conducted. The p-value was 0.016.
What should be our conclusions? - answer✔The evidence is pretty strong - there is a difference
in the proportion of Republicans between the two areas of town.
A major grocery store chain is trying to cut down on waste. Currently, they get peaches from
two different distributors, Whole Fruits and Green Grocer. Out of a two large shipments, the
manager randomly selects items from both suppliers and counts the number of items that are
not sell-able due to bruising, disease or other problems. She then makes a confidence interval.
Is there a significant difference in the quality of the peaches between the two distributors?95%
CI for pW-pG:(0.064, 0.156) - answer✔We are 95% confident that the proportion of non sell-
able items for Whole Fruits is anywhere between 0.064 and 0.156 HIGHER than the proportion
of non sell-able items for Green Grocer.
Which of the following are assumptions for the confidence interval for the different between
two population means? - answer✔Both sample sizes are greater than 30 or the data from a
Normal Distribution
Data is Quantitative.
Random Sample
Do men and women save different amounts of money? A study asks 100 randomly selected
men and women between the ages of 25 and 60, "How much they saved in a savings account or
similar type account in the past six months?" How should we write the alternative hypothesis?
Let mum = population mean amount saved for men and muw = population mean amount saved
for women. - answer✔Ha: mum - muw does not equal 0
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