stat exam 3 – Flashcards

Which of the following best describes correlation? A) Correlation measures the strength of the relationship between two quantitative variables whether or not the relationship is linear B) Correlation measures how much change in the explanatory variable causes a change in the response variable. C) Correlation measures the strength of the relationship between any two variables. D) Correlation measures the strength of the linear relationship between two quantitative variables. E) Correlation measures the strength of the linear association between two categorical variables.

Which of the following statements about causation and association is (are) FALSE? A) Some observed associates between two variables are due to a lurking variable rather than a cause-and-effect relationship between the two variables. B) Some possible explanations of an observed assocation are (1) causation, (2) common response, or (3) confounding C) When many variables interact with each other, confounding of several variables often prevents a conclusion about causation to be reached. D) To establish that association is due to causation it is best to conduct an experiment that makes changes to the explanatory variable while controlling other influences on the response variable. E) When strong association between two variables is present, this is often sufficient evidence to establish that the association is because of a causal link.

The correlation between two variables x and y is r = 0.121. What conclusion can we draw? A) Because the correlation is so low, the relationship between x and y is not very strong, thus there is no use in studying this relationship B) Because the correlation is so low, we only know that the linear relationship between x and y is not very strong, but there may be a different relationship between the two variables. We need to first look at a scatterplot. C) The correlation between x and y is low, but that does not matter. We can still use least-squares regression to calculate an equation of the form y-hat = ax +b D) None of the above

A study found a correlation of r = -0.61 between the gender of a worker and his or her income. Which statement is TRUE? A) Women earn more than men on the average. B) Women earn less than men on the average. C) An arithmetic mistake was made. Correlation must be positive. D) This measurement makes no sense; r can only be measured between two quantitative variables.

Correlation is a measure of the direction and strength of the linear (straight-line) association between two quantitative variables. The analysis of data from a study found that the scatterplot between two variables, x and y, appeared to show a straight-line relationship and the correlation was calculated to be -0.84. This tells us that A) There is little reason to believe that the two variables have a linear association relationship. B) All of the data values for the two variables lie on a straight line. C) There is a strong linear relationship between the two variables with larger values of x tending to be associated with larger values of the y variable. D) there is a strong linear relationship between x and y with smaller x values tending to be associated with larger values of the y variable. E) there is a weak linear relationship between x and y with smaller x values tending to be associated with smaller values of the y variable.

Researchers studied a sample of 100 adults between the ages of 25 and 35 and found a strong negative correlation between the amount of vitamin C an individual consumed and the number of pounds the individual was overweight. Which of the following can we conclude? A) This is strong, but not conclusive, evidence that large amounts of vitamin C inhibit weight gain. B) If the amount of vitamin C consumed and the number of pounds overweight for each individual in this study were plotted on a scatterplot, the points would lie close to a negatively sloping straight line. C) If the amount of vitamin C consumed and the number of pounds overweight for each individual in this study were plotted on a scatterplot, the points would lie close to a positively sloping straight line. D) All of the above.

An electronics store is handing out a survey to their clients who buy a DVD player. Some of the questions on the survey ask the clients to rate the DVD player on ease of use, appearance, price, etc. Another question asks for the client's age. From all the different ratings on the survey, a total assessment score is calculated. The correlation between this total assessment score and age of the client is -0.165. The store owner can legitimately conclude which of the following? A) OlderclientsseemnottolikeDVDplayers. B) Thereisanegativelinearrelationshipbetweenageand assessment score. C) Agedoesnothelpmuchinpredictingassessmentscore. D) Noneoftheabove.Wereallyneedtolookatascatterplotof the data first.

The least-squares regression line is fit to a set of data. One of the data points has a positive residual. Which statement is true? A) The correlation between the values of the values of the response and explanatory variables must be positive. B) The point must lie above the east-squares regression line. C) The point must lie near the right edge of the scatterplot. D) The point must be influential.

The level of calcium in the blood of healthy young adults follows a Normal distribution with mean μ = 10 milligrams per deciliter. Doctors are interested to know if the mean calcium level is less than this for young pregnant women. H0: μ=10 vs Ha: μ<10 They collect a random sample of 25 healthy pregnant young women and calculate a sample mean of 9.8 milligrams per deciliter, with a standard deviation of 0.4 milligrams per deciliter. The p-value is 0.0098. At a 5% significance what is your conclusion? A) There is sufficient evidence that the level of calcium in the blood is 10 milligrams per deciliter. B) There is sufficient evidence that the level of calcium in the blood is less than 10 milligrams per deciliter. C) There is insufficient evidence to say that the level of calcium in the blood is 10 milligrams per deciliter. D) There is insufficient evidence to say that the level of calcium in the blood is less than 10 milligrams per deciliter.