A company has only one cafeteria, which provides food for all of its employees, who come from many different cultures and ethnic groups. What would be the most reccomended sampling technique in studying the opinions on which foods should be sold in the cafeteria?
stratified sample
100
A tutor wants to compare the IQ levels of her younger students (elementary schoolers) versus her older students (high schoolers). Which of the following graphical displays is inappropriate?
Scatterplots
100
60% of students pass their AP stats exam. In a group of 30 people, what's the probablility that more than half pass the exam?
P(x>15)
binomcdf(20,.6,15)=.1753
100
Any outcome or set of outcome of a random phenomenon
What is an event
100
In general, how does doubling the sample size change the confidence interval size?
A. Divides the interval size by 1.414
B. Halves the interval size
C. Doubles the interval size
D. All the above
E. None of the above
A. Divides the interval size by 1.414
200
Suppose you want to compare the average points scored by varsity basketball players to the average points scored by the junior varsity basketball players at your high school. What technique would be most appropriate for collecting the data?
Census
200
If quartiles Q1=20 and Q3=70, which of the following must be true?
I. Median is 30
II. Mean between 20 and 40
III. Standard deviation is at most 20
II
200
43% of teens say they have trouble with homework. If a teacher contacts an SRS of 50 people, what's the probability more than 45% will say they have trouble with homework?
standard deviation=√(.43)(1-.43)/50=.07
normal cdf(.45,1,.43,.07)=.3875
200
Variable that requires a fixed amount of trials
What is binomial random variable
200
When making an inference about a population mean, which of the following suggests the use of t-scores rather than z-scores?
A. Outliers are absent
B. Sample size is under 30
C. The population standard deviation is unknown
D. Population is Normal
E. Strong skew is absent
C. The population standard deviation is unknown
300
A marketing firm conducts weekly surveys to determine the proportion of adults aged 30-40 who are familiar with their product. For the third year that they use a survey they decide to triple the sample size. What is the main benefit of increasing the sample size?
Decrease the standard deviation of the sampling distribution
300
When a distribution has many gaps and clusters in it, which can give the best overall description of the set of data?
Stemplot
300
A person has a 13% chance of beating someone in a race. What is the probability he wins on the third day?
(.87)(.87)(.87)(.13)=.098
300
Estimate ± margin of error
What is confidence interval
300
A researcher believes that a new diet should improve weight gain in laboratory mice. If the average gain for 13 mice on a new diet is 6.3 oz with a standard deviation of .9 ounces, while 16 control mice on the old diet gain an average of 6 ounces with a standard deviation of .8 ounces. What is the p-value?
p-value=.178
400
A car dealership plans to survey 200 of the 8,000 customers they have had thus far. An alphabetical list of customers is given and a random number between 1 and 40 us picked. The sample consists of the person in which the random number is assigned along with every 40th person after that. Which type of sampling is this procedure an example of?
Systematic
400
Suppose that the scatterplot of log x and log y shows a strong positive correlation close to 1. Which of the following is true?
I. A scatterplot of the variables x and y will show a nonlinear pattern
II. The residual plot of the variables shows a random pattern
III. Both individual variables also have a correlation close to one.
I. A scatterplot of the variables x and y will show a nonlinear pattern
400
According to a magazine, 12% of people say they like cheese. In an SRS of 15 people, what is the probability at least one person likes cheese?
P(at least one)=1-P(none)=1-(.88)^15=1-.527
=.853
400
What is the formula for calculating a test statistic?
Estimate-hypothesized value/standard deviation of estimate
400
The school superintendent wants to know what percent of property owners are willing to support an increase in school taxes. What size sample should be obtained to determine with 95% confidence the support level within 5%?
A. 33
B. 120
C. 384
D. 400
E. 1000
C. 384
500
To find out the amount of school dances the average student at his high school attends. George interviews a random sample of students arriving at homecoming. The average number of dances at the end of the night is 12.6. Is this estimate most likely too low or too high?
Too high
500
Suppose the number of marbles in a bag have a mean of 75 marbles with a standard deviation of 8. One bag has a z-score of -1.5 and another has a z-score of 2.0. How many more marbles did the second bag have?
28
500
If P(A)=.30 and P(B)=.33, what is the P(A or B), if A and B are independent?
P(A or B)=P(A)+P(B)-P(A) x P(B)
=.30+.33-(.30)(.33)=.531
500
What are the 2 rules of thumb used for sample proportions?
Rule of Thumb #1: Use the recipe for the standard deviation of p-hat only when the population is at least 10 times as large as the sample. That is, when N≥10n.
Rule of Thumb #2: We will use the Normal approximation to the sampling distribution of p-hat for values of n and p that satisfy np≥10 and n(1-p)≥10.
500
A principal at Chanhassen High School is informed that among 1,450 students in her high school, the average GPA is 2.83 with standard deviation of .52. With what margin of error is the mean GPA of these students known?