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**Unformatted text preview: **6/6/2016 Quiz Feedback Print Quiz, Introduction to Statistical Concepts Your Score: 90% Congratulations! Your score of 90% indicates that you've mastered the topics
in this lesson. If you'd like, you can review the feedback for each question. 1. For an asymmetric (or skewed) distribution, which of the following statistics is a good
measure for the middle of the data? a. mean b. median c. either mean or median
Your answer: b Correct answer: b The median is not affected by outliers and is less affected by the skewness. The mean,
on the other hand, averages in any outliers that might be in your data. 2. Which of the following code examples correctly calculates descriptive statistics of
popcorn yield (Yield) for each level of the class variable (Type) in the data set
Statdata.Popcorn, as well as statistics for all levels combined?
The output should include the following statistics: sample size, mean, median, standard
deviation, variance, range, and interquartile range. a. proc means data=statdata.popcorn maxdec=2 fw=10 n mean median std var range qrange; class Type; var Yield; run; b. proc means data=statdata.popcorn maxdec=2 fw=10 printalltypes n mean median std var range qrange; class Yield; var Class; run; c. proc means data=statdata.popcorn maxdec=2 fw=10 printalltypes n mean median std var range qrange; class Type; 1/5 6/6/2016 Quiz Feedback var Yield; run; d. proc means data=statdata.popcorn maxdec=2 fw=10 printalltypes n mean median std range IQR; class Type; var Yield; run; Your answer: c Correct answer: c The PROC MEANS statement must include the option PRINTALLTYPES in order for SAS
to display statistics for all requested combinations of class variables – that is, for each
level or occurrence of the variable and for all occurrences combined. The statistics
specified on the second line must include the keywords N MEAN MEDIAN STD VAR
RANGE QRANGE. The code must specify Type as the class variable and Yield as the
analysis variable. 3. Read the following statement about the central limit theorem and choose the answer that
contains the correct values for all of the missing fields.
The central limit theorem states that the distribution of sample __(1)__ is approximately
__(2)__, regardless of the distribution of the population data, and this approximation
improves as the sample size gets __(3)__. a. b. c. d. means, skewed, larger
variance, equal, smaller
means, normal, larger
proportions, equal, smaller Your answer: c Correct answer: c The central limit theorem states that the distribution of sample means is approximately
normal, regardless of the distribution of the population data, and this approximation
improves as the sample size gets larger. 4. Psychologists at a college want to know if students are sleeping more or less than the
recommended average of 8 hours a day.
Which of the following code choices correctly tests the null hypothesis? a. proc univariate data=statdata.sleep mu0<>8; var hours; run; b. proc univariate data=statdata.sleep; 2/5 6/6/2016 Quiz Feedback var hours / mu0=8; run; c. proc univariate data=statdata.sleep; var hours / mu0<>8; run; d. proc univariate data=statdata.sleep mu0=8; var hours; run; Your answer: d Correct answer: d You specify the MU0= option as part of the PROC UNIVARIATE statement to indicate the
test value of the null hypothesis. The alternative hypothesis is that μ is not equal to 8
hours, but this does not need to be specified in the PROC UNIVARIATE code. 5. How do you define the term power? a. the measure of the ability of the statistical hypothesis test to reject the null
hypothesis when it is actually false b. the probability of committing a Type I error c. the probability of failing to reject the null hypothesis when it is actually false
Your answer: a Correct answer: a Power is the ability of the statistical test to detect a true difference, or the ability to
successfully reject a false null hypothesis. The probability of committing a Type I error is
α. The probability of failing to reject the null hypothesis when it is actually false is a Type
II error. 6. Select the choice that lists only continuous variables. a. b. c. d. body temperature, number of children, gender, beverage size
age, body temperature, gas mileage, income
number of children, gender, gas mileage, income
gender, gas mileage, beverage size, income Your answer: d Correct answer: b The continuous variables are age, body temperature, gas mileage, and income. 3/5 6/6/2016 Quiz Feedback 7. Which of the following code choices creates a histogram for the variable Speed from the
data set SpeedTest with a normal curve overlay and a box with the skewness and
kurtosis statistics printed in the northeast corner? a. proc univariate data=statdata.speedtest; histogram Speed / normal(mu=est sigma=est); inset skewness kurtosis; run; b. proc univariate data=statdata.speedtest; histogram Speed / normal; inset skewness kurtosis / position=ne; run; c. proc univariate data=statdata.speedtest; histogram Speed / normal(mu=est sigma=est); inset skewness kurtosis / position=ne; run; d. proc univariate data=statdata.speedtest; histogram Speed / normal(skewness kurtosis); run; Your answer: c Correct answer: c In the HISTOGRAM statement, you specify the Speed variable and the NORMAL option
using estimates of the population mean and the population standard deviation. In the
INSET statement, you specify the keywords SKEWNESS and KURTOSIS, as well as the
POSITION=NE option. 8. Select the statement below that incorrectly interprets a 95% confidence interval (15.02,
15.04) for the population mean, if the sample mean is 15.03 ounces of cereal. a. You are 95% confident that the true average weight for a box of cereal is between
15.02 and 15.04 ounces. b. The probability is .95 that the true average weight is between 15.02 and 15.04
ounces. c. In the long run, approximately 95% of the intervals calculated with this procedure
will capture the true average weight.
.
Your answer: b Correct answer: b A 95% confidence interval means that you are 95% confident that the interval contains
the true population mean. If you sample repeatedly and calculate a confidence interval for
each sample mean, 95% of the time your confidence interval will contain the true
population mean. A confidence interval is not a probability. When a confidence interval is
calculated, the true mean is in the interval or it is not. There is no probability associated
with it. 4/5 6/6/2016 Quiz Feedback 9. The location and spread of a normal distribution depend on the value of which two
parameters? a. b. c. d. the mean (x̄
) and the standard deviation (s)
the standard deviation (σ) and the variance (σ²)
the mean (µ) and the standard deviation (σ)
none of the above Your answer: c Correct answer: c The location and spread of a normal distribution depend on the value of two parameters,
the mean (µ) and the standard deviation (σ). 10. The standard error of the mean is a. b. c. d. used to calculate confidence intervals of the mean.
always normally distributed.
sometimes less than 0.
none of the above Your answer: a Correct answer: a The standard error of the mean is part of the equation used to calculate a confidence
interval of the mean. It is not normally distributed, and it is never less than 0. Close Copyright © 2016 SAS Institute Inc., Cary, NC, USA. All rights reserved. 5/5 ...

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- Summer '16
- naveen rathi
- Mean, Correct Answer, Mean Median Std