staticstics
For left skewed, the mean is less than the median A. True B. False
a
Where do we locate a z-score in the Standard Normal table? A. In the left and top margins of the table B. In the inside of the table C. In the right and bottom margins of the table
a
For right skewed, the mean is less than the median A. True B. False
b
Z-scores measure _______________. Please choose the correct answer from the following choices, and then select the submit answer button. a. how far the value is from the mean in units of the original variable. b. the proportion of observation less than a particular value. c. how far the value is from the mean in units of standard deviation (σ). d. how far the value is from the mean in units of standard deviation (s)
c
A z-score of -0.67 has 25% of the area less than it and 75% of the area greater than it. What do we call this value? A. Q3 B. Median C. Mean D. Q1
d
A good use of z-scores is to compare values in two different distributions. Suppose your instructor will drop the low test when computing final grades, but he curves grades on each test. You had a 92 on the first test, and an 85 on the second. The first test had a mean of 83 and standard deviation of 6. The second test had a mean of 75 and standard deviation 3. The z-score for your second test is ______. a. 3.33 b. 3.53 c. 4.00 d. 2.22 e. 3.00
a
If a z-score is negative, the area to its right is greater than 0.5. Please choose the correct answer from the following choices, and then select the submit answer button. a. True b. False
a
In order to find the z-score with 90% of the area to its right, what cumulative area should you look up? A. 0.1000 B. 0.9000 C. 0.0500 D. 0.9500
a
If the density curve is symmetric, then the mean is ____________ the median. A. less than B. equal to C. greater than Submit
b
In order to find the z-score with 90% of the area to its right, what cumulative area should you look up? A. 0.0500 B. 0.1000 C. 0.9500 D. 0.9000
b
Attendance at a university's basketball games follows a Normal distribution with mean μ = 8,000 and standard deviation σ = 1,000. The attendance at 95% of all games will be between __________ . Please choose the correct answer from the following choices, and then select the submit answer button. a. 7,000 and 9,000 people b. 5,000 and 11,000 people c. 6,000 and 10,000 people d. 4,000 and 12,000 people
c
IQs as measured by the Wechsler Adult Intelligence Scale are approximately Normal with mean 100 and standard deviation 15. About what percent of adults will have IQs at least 85? Use the 68-95-99.7% rule and give your final answer as a whole number a. 16 b. 80 c. 84 d. 75
c
If the density curve is left-skewed, then the mean is ____________ the median. A. equal to B. greater than C. less than
c
If the density curve is right-skewed, then the mean is __________ the median. A. less than B. equal to C. greater than
c
In order to find the z-scores with middle area of 60% symmetric about µ = 0, what cumulative area should you look up? A. 0.4000 B. 0.8000 C. 0.2000 D. 0.6000
c
What is the name of the density curve that models many bell-shaped symmetric distributions? A. Poisson distribution B. Exponential distribution C. Binomial distribution D. Normal distribution E. Gamma distribution Submit
d
True or false: The Standard Normal table gives both areas to the right and areas to the left. A. True B. False
b
A good use of z-scores is to compare values in two different distributions. Suppose your instructor will drop the low test when computing final grades, but he curves grades on each test. You had a 92 on the first test, and an 85 on the second. The first test had a mean of 83 and standard deviation of 6. The second test had a mean of 75 and standard deviation 3. The test with the relatively better score is ____________. a. Test 2 b. Test 1
a
After we locate the cumulative area inside the Standard Normal table, where do we locate the corresponding z-score? A. In the left and top margins of the table B. In the right and bottom margins of the table C. In the inside of the table Submit
a
True or false: Areas given by the Standard Normal Table are cumulative proportions. A. True B. False
a
What symbol represents the standard deviation of a sample? A. x̄ B. σ C. μ D. s
d
Most computer random number generators (at least initially--we can build others based on this) give random numbers uniformly distributed between 0 and 1. That is, any number between 0 and 1 is equally likely to occur. The mean of this distribution will be ______. a. 0.5 b. 0.4 c. 0.6 d. 1 e. 0
a
Three Normal distributions all have mean 20. Distribution A has standard deviation 1, distribution B has standard deviation 5, and distribution C has standard deviation 10. The distribution with the sharpest peak is distribution ___.
a
True or False: If the area to the right of a z-score is less than 0.5, the z-score is negative. Please choose the correct answer from the following choices, and then select the submit answer button. a. False b. True
a
True or False: The quartiles of any Normal distribution are located about 0.675 standard deviations from the mean. a. True b. False
a
True or False: The z-score that has area 0.67 to its right is 0.44. Please choose the correct answer from the following choices, and then select the submit answer button. a. False b. True
a
True or false: Before finding a z-score for a given area, you should always convert the given area to a cumulative area if it is not already a cumulative area. A. True B. False
a
True or false: Density curves are smooth curves that follow the shape of the corresponding histogram. A. True B. False
a
True or false: Density curves are smooth curves that follow the shape of the corresponding histogram. A. True B. False Submit
a
True or false: The area under the Standard Normal table gives the proportion of observations in that interval. A. True B. False
a
True or false: The distance from the mean to the largest observation of a Normal distribution is equal to standard deviation. A. False B. True
a
True or false: To find a z-score in the Standard Normal table, just look up the given proportion inside the table and read the z-score in the top row and left column. A. False B. True
a
True or false: You can only use the Standard Normal table to find cumulative proportions. A. False B. True
a
True or false: the mean is the point of symmetry of a Normal distribution. A. True B. False
a
Use the standard Normal table (use the table reader, the table in your textbook, or a graphing calculator) to find the area between the following two z-scores: -1.98 and 0.50. Round your answer to four decimal places. a. 6676 b. 6915 c. 0239 d. 6728
a
What is standardizing? A. Measuring in standard deviation units from the mean. B. Finding the area under a Normal curve in a specified interval. C. Subtracting the standard deviation from each value.
a
What is the first step in finding an area under a Normal distribution for an x-value using the Standard Normal table? A. Compute the z-score for the x-value. B. Find the x-value on the appropriate table. C. Use the 68-95-99.7 rule
a
When given a cumulative proportion and asked for the corresponding z-score, how do we use the Standard Normal Table? A. Look for the cumulative proportion in the center of the table and read the z-score in the margins. B. Look for the z-score in the margins and find the proportion in the center of the table. Submit
a
Which is a valid property of a density curve? A. Total area under the curve is 1.00 (or 100%) B. Proportion of values in an interval is given by counting the number of X values in that interval and dividing by the total number of X values. C. Curve that goes above and below the x-axis
a
Which mease of center represents the balance point of the density curve A. Mean B. Median
a
Which measure of center is the point at which the area of the density curve is cut in half vertically? A. Median B. Mean
a
Why is drawing the Normal curve and shading the desired area important? A. To know whether you want area on the left, on the right or between two x-values. B. To give students practice in drawing Normal curves. C. To help find the height corresponding to the x-value.
a
fter we locate the cumulative area inside the Standard Normal table, where do we locate the corresponding z-score? A. In the left and top margins of the table B. In the inside of the table C. In the right and bottom margins of the table
a
Attendance at a university's basketball games follows a Normal distribution with mean μ = 8,000 and standard deviation σ = 1,000. Use the 68-95-99.7 Rule to estimate the percentage of games that have between 7,000 and 10,000 people in attendance. a. 81 b. 81.5 c. 80.5 d. 80 e. 79.5
b
Fill in the blank: The shape of the Standard Normal distribution is ____________ the shape of a Normal distribution with mean, µ = 20 and standard deviation, σ = 8. A. more skewed, but with less spread than B. bell-shaped, but taller and skinnier than C. bell-shaped with the same spread as D. bell-shaped, but shorter and flatter than
b
How do you find area to the right of a z-score using a cumulative proportion? A. Add the cumulative area on the left of a z-score to the cumulative area on the right. B. Subtract the cumulative area for the z-score from 1.0. C. Simply find the cumulative area.
b
In order to find the z-score with 40% of the area to its left, what cumulative area should you look up? A. 0.6000 B. 0.4000 C. 0.8000 D. 0.2000
b
In order to find the z-score with 40% of the area to its left, what cumulative area should you look up? A. 0.8000 B. 0.4000 C. 0.2000 D. 0.6000
b
The length of human pregnancies from conception to birth is known to be normally distributed with a mean of 266 days and standard deviation of 16 days. A "nine month" pregnancy might be considered as 274 days (four months have 30 days, and February has 28 in most years). What proportion of pregnancies last less than "9 months"? Answer to four decimal places. You will need to use the table in the textbook. a. .3085 b. .6915 c. .7101 d. .5941
b
To find area on the left for a z-score using the Standard Normal table, what should one do? A. Look up the z-score and subtract the corresponding cumulative area from 1.0. B. Simply look up the z-score C. Look up both z-scores and subtract the smallest cumulative area from the largest.
b
True or False: It appears that people who are mildly obese are less active than leaner people. One study looked at the average number of minutes per day that people spend standing or walking. Among mildly obese people, minutes of activity is normally distributed with mean 373 minutes and standard deviation of 67 minutes. The least active 20% of these individuals spend at most 310.5 minutes walking or standing. a. True b. False
b
True or False: Mensa is a society for "geniuses." One way to qualify for membership is having an IQ at least 2.5 standard deviations above average. One typical IQ scale has a mean of 100 and standard deviation 15. Having an IQ of 140 on that IQ scale will qualify a person for membership in Mensa. a. False b . True
b
True or false: For density curves the height of the curve at a particular X-value equates to the proportion of values in the population that have that X value. A. True B. False
b
True or false: If an x variable has a Normal distribution, then z = (χ−μ)σ(χ−μ)σ has a Standard Normal distribution. A. False B. True Submit
b
True or false: The symbol for the mean of a population, and for the mean of a sample, are the same. A. True B. False
b
True or false: To find a z-score in the Standard Normal table, just look up the given proportion inside the table and read the z-score in the top row and left column. A. True B. False
b
True or false: We use the table for the Standard Normal distribution to get areas for any Normal distribution. A. False B. True
b
What does a z-score tell us? A. The number of standard deviation distances along the x-axis of a Normal curve B. How many standard deviations an x-value is from the mean C. How far an x-value is from the mean
b
Where are the ones and tenths digits of a z-score given in a Standard Normal curve? A. In the right hand column B. In the left hand column C. Across the top D. Across the bottom
b
Where do we locate a proportion (area) in the Standard Normal table? A. In the left and top margins of the table B. In the inside of the table C. In the right and bottom margins of the table
b
Where do we locate the cumulative area in order to find a z-score? A. In the right and bottom margins of the table B. In the inside of the table C. In the left and top margins of the table
b
Where do we locate the cumulative area in order to find a z-score? A. In the left and top margins of the table B. In the inside of the table C. In the right and bottom margins of the table
b
Which measure of center represents the balance point of the density curve? A. Median B. Mean
b
Which of the following is NOT a characteristic of a Normal distribution? A. Mean equals median B. Two peaked C. Symmetric D. Bell-shaped
b
Why do we model data with a density curve? A. To identify outliers B. To estimate probabilities of various outcomes. C. To make it easier to find sample means and standard deviations.
b
1st step in exploring data A. To identify outliers B. To estimate probabilities of various outcomes. C. To plot the data D. To make it easier to find sample means and standard deviations.
c
A z-score of -0.67 has 25% of the area less than it and 75% of the area greater than it. What do we call this value? A. Mean B. Q 3 C. Q1 D. Median
c
Approximately how many standard deviation distances are on either side of the mean? A. One B. Four C. Three D. Two
c
In order to find the z-scores with middle area of 60% symmetric about µ = 0, what cumulative area should you look up? A. 0.6000 B. 0.8000 C. 0.2000 D. 0.4000
c
Rachael got a 550 on the analytical portion of the Graduate Record Exam (GRE). If GRE scores are normally distributed and have mean μ = 600 and standard deviation σ = 30, what percent of students score better than she did? a. 90.00% b. 85.15% c. 95.15% d. 80.54%
c
The length of human pregnancies from conception to birth is known to be normally distributed with a mean of 266 days and standard deviation of 16 days. A pregnancy longer than "nine months" might be considered as 274 days or longer (four months have 30 days, and February has 28 in most years). What proportion of pregnancies last more than "9 months?" a. .6915 b. .2511 c. .3085 d. .2935
c
To find area between two z-scores using the Standard Normal table, what should one do? A. Look up the z-score and subtract the corresponding cumulative area from 1.0. B. Simply look up the z-score C. Look up both z-scores and subtract the smallest cumulative area from the largest. Submit
c
To find area on the right for a z-score using the Standard Normal table, what should one do? A. Simply look up the z-score B. Look up both z-scores and subtract the smallest cumulative area from the largest. C. Look up the z-score and subtract the corresponding cumulative area from 1.0.
c
What area is given by a cumulative proportion? A. Area on the right B. Height of the curve C. Area on the left
c
What is the key to finding Normal proportions? A. Plug the x-value into the formula for the curve to find the proportion. B. Square the distance from the x-value to the mean. C. Match the area you need with a cumulative proportion.
c
What part of a z-score is given by the values in the top row of a Standard Normal curve? A. The ones digit B. The tenths digit C. The hundreths digit
c
What symbol represents the density curve (population) standard deviation? A. μ B. x̄ C. σ D. s
c
What symbol represents the mean of a sample? A. μ B. σ C. x̄ D. s
c
What symbol represents the mean of the density curve (population mean)? A. σ B. x̄ C. μ D. s
c
Which of the following statements concerning areas under the standard Normal curve is true? Please choose the correct answer from the following choices, and then select the submit answer button. a. If a z-score is positive, the area to its left is less than 0.5 b. If the area to the right of a z- score is less than 0.5, the z-score is negative. c. If a z-score is negative, the area to its right is greater than 0.5.
c
It appears that people who are mildly obese are less active than leaner people. One study looked at the average number of minutes per day that people spend standing or walking. Among mildly obese people, minutes of activity is normally distributed with mean 373 minutes and standard deviation of 67 minutes. The least active 20% of these individuals spend at most how many minutes walking or standing? a. 419.6 b. 429.4 c. 310.5 d. 316.7
d
Mensa is a society for "geniuses." One way to qualify for membership is having an IQ at least 2.5 standard deviations above average. IQs are approximately Normally distributed, according to the WAIS scale. What percent of people should qualify? a. 2.5% b. 1.5% c. .5% d. .62%
d
Mensa is a society for "geniuses." One way to qualify for membership is having an IQ at least 2.5 standard deviations above average. IQs are approximately Normally distributed, according to the WAIS scale. What percent of people should qualify? a. 59.87% b. 99.38% c. 6.2% d. 0.62%
d
The distribution of bladder volume in men is approximately Normal with mean 550 ml and standard deviation 100 ml. What proportion of men has a bladder volume larger than 450 ml? a. 16% b. 97.5% c. 68% d. 84%
d
The tallest person ever confirmed by the Guinness records organization was Robert Wadlow of the United States, at 8 feet 11.1 inches tall. Heights of American men are approximately Normal with mean 69.3 inches and standard deviation 2.8 inches. What is Wadlow's z-score? Round your answer to one decimal place. a. 2.5 b. 3.9 c. 14.2 d. 13.5
d
What is the mean of the Standard Normal distribution? A. 2 B. 3 C. 1 D. 0
d
What is the standard deviation of the Standard Normal distribution? A. 3 B. 0 C. 2 D. 1
d
Which of the following characterize a Normal distribution? A. Mean and interquartile range B. Mean and median C. Median and interquartile range D. Mean and standard deviation
d
Which of the following is a way to find areas other than 68-95-99.7 for a Normal distribution? A. Iterate using the 68-95-99.7 numbers B. Use the Standard Normal table C. Use statistical software D. Both A and B E. Both A and C F. Both B and C
f
