Sampling and Bias
Which word has this definition- (size N) Entire collection of individuals you wish to study
.a. Sample
b. Statistics
c. Parameters
d. Population
population
A sample of students was asked what major they planned to study. Which of the following types of graphical display would be appropriate for the sample?
A. Pie chart B. Histogram C. Stemplot D. All are appropriate
Pie chart
Which of the following types of graphical display would be appropriate for a sample of student heights?
A. Pie chart
B. Scatterplot
C. Stemplot
D. All of the above since we are dealing with numbers.
C. Stemplot
True or False - The IQR is not resistant to outliers
False
If P(A) = 0.30 and P(B) = 0.20, what is P(A or B) if A and B are independent?
A. 0.06
B. 0.44
C. 0.50
D. 0.56
E. None of these
B. 0.44
You are trying to determine the average age of runners at SDSU. The average age of 45 randomly selected runners is 18. 18 is described as:
a. Statistic
b. Parameter
c. Sample
d. Population
statistic
If the standard deviation of a sample is zero, which of the following must be true?
A. The mean must also equal zero
B. The sample values are all equal
C. The median must equal zero.
D. Both A. and B. are true.
b. the sample values are all equal
All of the following are examples of categorical data, except:
A. favorite color.
B. Income
C. gender
D. Final letter grade in a course (A, B, C, D, F)
B. Income
8. Which of the following statements are true? I. A residual plot with no pattern indicates poor predictive power. II. A point is influential if removing it changes the regression model.
A. I only
B. II only
C. I & II
D. Neither is true
B. II only
The probability of event A is 0.4. The probability of event B is 0.6. If events A and B are disjoint, then: A. P(A or B) =1.0
B. P(A and B) = 0.24
C. P(A or B) = 0.76
D. P(A or B) = 0
A. P(A or B) =1.0
Is the following statement true or false: Parameters are measurements made on sample data. Must include why for full credit.
False because parameters are measurements made on population
In a study of credit card charges, the distribution was found to be right skewed with several high outliers. What would be the appropriate measure of spread for this distribution? Why (needed for full credit)?
IQR, because the data is skewed
Two events, X and Y, are independent, such that P (Y) = 0.52 and P (X) = 0.41. What is the value of P(X or Y)?
A. 0.7168
B. 0.9300
C. 0.2132
D. 0.1100
A. 0.7168
A physician found that the correlation coefficient between the time adults spend exercising each day and a numerical rating of heart health is 0.9. This suggests that
A. 90% of adults who exercise daily have healthy hearts
B. There is no association between time spent exercising and heart health
C. There is a strong negative linear association between time spent exercising and heart health
D. The coefficient of determination for this relationship is 81%
D. The coefficient of determination for this relationship is 81%
A gaming website found that 65% of individuals own a PS4, 15% own an Xbox One, and the rest own a Wii U. Assume that owners of each console are independent. Suppose three people were randomly selected: a) Find the probability all three individuals own a Wiii U
.008
An experiment is being performed to test the effects of alcohol on reaction time. Subjects were selected at random and given three beers to consume. Their reaction time to a simple stimulus was measured before and after drinking the alcohol. What type of experimental design is this?
Matched Pair
True or False - If the mean of a data set is smaller than the median then the data set is right skewed. Must explain for full points
False, the mean always moves in the direction of the skew
An athlete completed an 800-m race in 140 seconds. The distribution of 800-m race times followed a bell curve, with mean 150 seconds and standard deviation 6. The same athlete also competed in a swim, finishing in 10.25 minutes. The distribution of swim times also followed a bell curve, with mean 12 minutes and standard deviation 1.5 minutes. In which event does the athlete have a better standing relative to the other competitors in the event?
A. The 800-m race because that has the higher z-score.
B. The swim because that has the higher z-score
C. The 800-m race because that has the lower z-score
D. The swim because that has the lower z-score
E. The athlete has the same standing in both events.
C. The 800-m race because that has the lower z-score
A researcher uses a regression equation to predict home energy bills (dollar cost), based on home size (square feet). The correlation between predicted bills and home size is 0.68. What is the correct interpretation of this finding?
A. For each added square foot of home size, energy bills increased by $0.68
B. For each added dollar of energy bill, home size increased by 0.68 square feet.
C. 46.24% of the variability in home energy bills can be explained by home size.
D. 46.24% of the variability in home size can be explained by home energy bills.
E. None of the above.
C. 46.24% of the variability in home energy bills can be explained by home size.
A gaming website found that 65% of individuals own a PS4, 15% own an Xbox One, and the rest own a Wii U. Assume that owners of each console are independent. Suppose three people were randomly selected:b) Find the probability at least one of the three owns a Wii U.
.488
In a survey to estimate potential voters support for the California ballot initiative, a random sample of registered voters in Los Angeles is selected. The most significant source of bias will be:
a. Undercoverage
b. Response bias
c. Non-response bias
Undercoverage
This is based off a sample of 41 adults. It was determined that the HIGH outlier resulted from a weight being incorrectly entered. The incorrect data point was removed from the data set and new summary statistics were calculated. Which of the following statements is true? When the incorrect data point is removed:
A. The mean and standard deviation will both be smaller.
B. The mean will be smaller, but the standard deviation will be larger.
C. The mean and standard deviation will both be larger.
D. The mean will be larger, but the standard deviation will be smaller.
A. The mean and standard deviation will both be smaller.
TRUE OR FALSE- A correlation of zero always means there is no linear relationship between x and y.
Recently, a group of adults who swim regularly for exercise were evaluated for depression. It turned out that these swimmers were less likely to be depressed than the general population. The researchers said the difference was statistically significant. What does the term statistically significant mean?
A. The difference in depression incidence for the two groups was small enough that it could be due to chance.
B. The difference in depression incidence for the two groups was large enough that it could not be due to chance.
C. The difference in depression incidence for the two groups was small enough that it could not be due to chance.
D. The difference in depression incidence for the two groups was large enough that it could be due to chance.
B. The difference in depression incidence for the two groups was large enough that it could not be due to chance.
Suppose 62% of college students have part-time jobs and 59% of college students have loans. 70% of the students who have loans have part time jobs. What is the probability a student selected at random has both a part-time job and a loan?
A. 0.3658
B. 0.413
C.0.434
D. 0.51
E. None of these
B.413
P(A|B)P(B)=.7*.59