Unit 1-2
Determine which variable is Quanitative?
Hair Color
Speed of a car
Shapes
Household Income
Dog Breeds
Population
Ethnicity
Gender
Exam Scores
speed of car
Household income
Population
Exam Scores
What problems arise when we collect samples?
sometimes the samples may not be representative of the whole population
The standard deviation of X is 0.9. Which of the following is the best interpretation of this value?
the number of puzzles solved by subjects typically differed from the mean by about 0.9 puzzles.
A researcher wants to do a study. He decides to use a convenience sample rather than a random sample because it is easier and less expensive. How does this choice affect his conclusion?
Generally whenever one deviates from using a random sample, the possibility of reaching a conclusion that is an error increases.
An owner of a movie theater is investigating whether critic rating can be used to predict the mean audience score of movies. Assuming the conditions for inference have been met, which of the following inference procedures is the most appropriate to estimate the mean change in audience score for each 1 point increase in the critic rating?
A linear regression tt-interval for slope
What is the mean of these values?
14,11,159,25,10,14
35.9
How does the way in which e collect data inform our analysis of the data?
a proper analysis of the data must take into account how the data was collected
Suppose a student is randomly selected from your school. Which of the following pairs of random variables are most likely independent?
X = average amount of homework the student does per night; Y = student's height
Using the P-value approach what is the comparison that reaches the conclusion: "reject H0"?
P-value < α
Assume that the conditions for inference for the slope of the regression equation have been met. Which of the following defines the margin of error of a 90 percent confidence interval for the slope of the least-squares regression line?
1.717(0.023)
A basketball player has scored 38 points, 32 points, and 45 points in his first three games.
In his next game, what is the minimum number of points he will need to score if he wants to bring his average (mean) up to 40 points per game?
45
What is the difference between an observational study and an experiment?
observational study: survey was taken without imposing treatments on individuals, can't infer cause and effect
- experiment: different conditions (treatments) are imposed upon subjects
Which of the following random variables is geometric?
the number of digits I read in a randomly selected row of the random digits table until I find a 7.
Can the two approaches of the previous problems ever lead to a different conclusion?
No, because P(Z > zc) is the same as α.
Russell plans on constructing a confidence interval for the slope of a regression line. He creates the residual plot shown to check the conditions for creating the interval. Which of the following conditions appear to be met based on the residual plot?
I only
Refer to the previous problem. On the final exam Carla scored 98. What is the value of her residual?
a. -2.5
b. 0
c. 2.5
d. 98
e. None of the above
c. 2.5
A business journal reports that the probability that Internet users in the United States will use a mobile payment app is 0.60. The journal claims this indicates that out of 5 randomly selected Internet users, 3 will use the mobile payment app.
Is the business journal interpreting the probability correctly?
No, because 0.60 represents probability in the long run for many Internet users.
The life span of a battery is the amount of time the battery will last. The distribution of life span for a certain type of battery is approximately normal with mean 2.5 hours and standard deviation 0.25 hour. Suppose one battery will be selected at random. Which of the following is closest to the probability that the selected battery will have a life span of at most 2.1 hours?
A.) 0.055
A bag of candy contains 5 different types of colored candies; red, green, blue, yellow, and orange. According to the manufacturer, bags should contain an equal number of each color. Students in a statistics class decided to use a chi-square procedure to test the manufacturer's claim. They opened a bag of candy and recorded the number of candies of each color. The results are shown in the following table. Which color contributes most to the chi-square test statistic?
Orange
The 98 percent confidence interval (−0.248,−0.134) was constructed to estimate the slope of a regression model for a bivariate data set with 20 values. Alice claims that a sample size of 25 will produce a narrower interval, all other things remaining the same. Desmond claims that a sample size of 15 will produce a narrower interval. Which statement is true about the claims made by Alice and Desmond?
Alice's claim is correct.
There is an approximate linear relationship between the height of females and their age (from 5 to 18 years) described by height = 50.3+6.01 (age) where height is measured in centimeters and age in years. Which of the following is not correct?
a. The estimated slope is 6.01, which implies that children increase by about 6 cm for each year they grow older.
b. The estimated height of a child who is 10 years old is about 110 cm.
c. The estimated intercept is 50.3 cm, which implies that children reach this height when they are 50.3/6.01=8.4 years old.
d. The average height of children when they are 5 years old is about 50% of the average height when they are 18 years old.
e. My niece is about 8 years old and is about 115 cm tall. She is taller than average.
c. The estimated intercept is 50.3 cm, which implies that children reach this height when they are 50.3/6.01=8.4 years old.
A certain spinner is divided into 6 sectors of equal size, and the spinner is equally likely to land in any sector. Four of the 6 sectors are shaded, and the remaining sectors are not shaded.
Which of the following is the best interpretation of the probability that one spin of the spinner will land in a shaded sector?
For many spins, the long-run relative frequency with which the spinner will land in a shaded sector is 2323.
The statistic ss is used as an estimator for which of the following?
A.) σ
B.) n
C.) z
D.) x¯
E.) μ
A.) σ
Which of the following best describes the shape of the chi-square distribution when the degrees of freedom are less than 10 ?
B. Skewed to the right
Sasha selected a random sample of bivariate data, with a sample size of 30, and calculated a slope of 3.6 for the sample slope of a regression model. Sasha constructed a 95 percent confidence interval to estimate the slope. Alex claims he can construct a confidence interval that is narrower by changing the sample size but keeping all other things the same. Which of the following sample sizes will make Alex's claim true?
35