stats final
Let Z be the random variable which has the standard normal distribution. Which of the following Excel functions will find P(Z < −0.65) ?
=NORM.DIST(-0.65, 0, 1, TRUE)
A sociologist wishes to test H0: µ =42 vs. Ha: µ<42. The sociologist takes a sample of size 100 and calculates a standardized test statistic of -2.34. To calculate a p-value for the test in Excel, the sociologist should use:
=NORM.DIST(-2.34,0,1,TRUE)
Which of the following Excel functions will find the critical value of Za/2 with the confidence level of 95%?
=NORM.INV(1-0.025, 0, 1)
410/1000
A company conducts a survey of 1000 randomly selected individuals to get their overall impressions of the past year. Results are shown below. What is the probability that the next person surveyed has a positive impression?
In a situation of hypothesis testing, what happens when the null hypothesis H0 is wrongly rejected when it is actually true?
A type 1 error occurs
19
A university dean wants to know how many credits students are taking. They randomly sample some students and put the results in the histogram below.
The score made by a particular student on a national standardized exam is the 75th percentile. This means that
About 75% of all scores on the exam were equal to or less than his.
The Department of Education wishes to estimate the proportion of all college students who have a job off-campus. It surveyed 1600 randomly selected students; 451 had such jobs. The population of interest to the Department of Education is:
All college students.
There were 1000 students who took part in the common final exam on STAT 1222. The average is 70 with a standard deviation 8. If a student got a z-score of 3.10 in this exam, which of the following is true?
Compared with other students in this exam, this student did extremely well.
Given a T distribution with the degrees of freedom of 16. Which function finds the probability that T is greater than 1.4?
DO NOT find your own degrees of freedom excell will do it for you =1-T.DIST(1.4, 16, TRUE)
The probability distribution of a discrete random variable X is given by x01234p(x) ? 0.30 0.10 0.20 0.10 Find the missing probability in the table.
Everything must add up to 1 so, .30
If every else remain the same which of the following confidence level will result the widest confidence interval?
Here 97% confidence interval is the widest confidence interval among all the following.
A diabetic claims that the average cost of insulin per year for a Type 1 diabetic is $5,605. She takes a sample of 100 Type 1 diabetics and finds their average cost is $5, 750 with a standard deviation of $370. Use =0.05 to test the claim. What are the hypotheses?
Ho: mu=5605 Ha: mu= DOES NOT=5605
Which equation should he use to construct the 95% confidence interval for the population mean waiting time?
If you are using population mean, u are trying to find mu so, use what you have (x bar) and follow a z score
The following two-way contingency table gives the breakdown of the voters in a particular locale according to gender and political party preference. A person is selected at random from this population. Let A be the event that the selected person will vote for Republican party; B be the event that the selected person is a Male. Find P ( A union B)
P(A∪B) = P(A) + P(B) - P(A∩B) P(A∪B) = 0.45 + 0.40 - 0.25
In the test of hypothesis H0:mu=100 vs . Ha: mu≠100, we already have the p-value for this test: P-value=0.025. Which of the following (with the reason) will be correct with significance level at .05?
Reject H0 since the P-value is less than the significance level.
Which of the following statements are true about the sampling distribution of x bar?
The mean of the sampling distribution is equal to the mean of the population.
Let Z be the random variable which has the standard normal distribution. Which of the following is NOT a property of the the standard normal distribution?
The potential values of Z are from-3 to 3 is not a properties of standard normal distribution because according to the Standard Deviation Rule, most of the area under the standardized curve falls between z = -3 and z = +3.
et X be the number you observe when you randomly roll a fair 6-sided die. An experiment consists of taking 1000 such rolls (i.e., sample size n = 1000). Let X bar be the average value of these 1000 rolls. Does X bar follow approximately a normal distribution?
Yes, True
In a random sample of 14 people, the mean body mass index (BMI) was 25.7 and the standard deviation was 5.12. Assume the body mass indexes are normally distributed. Which equation should he use to construct a confidence interval for the population mean BMI?
You have x bar (mean) and LOWER than n=30 so T score
A physician wanted to estimate the mean length of time that a patient had to wait to see him after arriving at the office. A random sample of 50 patients showed a mean waiting time of 30 minutes and a standard deviation of 9 minutes. Which equation should he use to construct the 95% confidence interval for the population mean waiting time?
You have x bar (mean) and above n=30 so Z score
The average sales price of single-family houses in Charlotte is $350,000 with a standard deviation of $40,000. A random sample of 100 single-family houses in Charlotte isselected. Let X bar represent the mean sales price of the sample. What is the mean of the sampling distribution?
Your mean of the average sale price is equal to the mean of the sampling distribution
The mean score on a standardized math exam is 75; the standard deviation is 8. Zack is told that the z-score of his exam score is -1.25. Which of the following statements is true?
Zack's score is below the class average.
Let x be a discrete random variable with the following probability distribution: Find P (x > -1)
add up p(x) values that are greater than -1.
What does the null hypothesis state?
always predicts whether your claim has no effect
what is a type 2 error?
everyone told me i was fine and not pregnant then I took a test 2 weeks later= I am pregnant
what is a type 1 error
false postive, if you are pregnant and the test says postive but you doctor say your are NOT pregnant.
If a new number (=11) is added to this data, what would happen to the mean? 8.6, 8.4, 9.3, 10.5, 9.8, 8.9, 10.2
it would increase
What does Fail to reject the null hypothesis mean?
meaning the test has NOT identified a consequential relationship between the two phenomena
A survey shows that people use cell phones an average of 1.6 years with a standard deviation of 0.3 years. A user is randomly selected. If cell phone use is normally distributed, we can use Excel to calculate the probability that the randomly selected user uses their phone for more than 1 year with the function:
more than means =1- NORM.DIST( 1, 1.6, 0.3, TRUE)
In the test of hypotheses H0: mu ≥100 vs Ha: mu < 100 . A sample of size 81 yields the standardized test statistic −1.50 . Which function in Excel finds the p-value?
n= 81 so norm.dist H0: mu ≥100 Greater than or equal to = 1-NORM.DIST ( -1.50, 0, 1, TRUE)
What score do you use If population under 30 and if population is over 30
over 30, z score under 30, t-score
Which function in Excel finds the p-value?
t.dist
Which tables give valid probability distribution for a discrete random variable?
tables must p(x) must add up to 1 or 100 and NO negatives (you can't have negative probability)
The level of significance (a) is
the maximum probability of making a Type I error
The level of significance is _______________.
the maximum probability of making a Type I error
What does reject the null hypothesis mean?
there IS a definite, consequential relationship between the two phenomena
The standard deviation of a data set measures the ___________ of the dataset.
variability
Norm. Inv is used when?
when you are given the probability on the left side and want to find what value of X reflects that probability.
Norm. Dist is used when ?
you want to find the probability of finding a value less than or equal to X
What is z score?
z score is how many stdev you way from the mean. If stdev is 8 and your z-score is 3.10, you are about 24 higher than the mean