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Q 1/13
Score 0
Which of the following is a defining feature of a normal distribution?
30
It is always skewed.
It has a symmetric, bell-shaped curve.
It consists only of whole numbers.
It has a uniform shape.
Q 2/13
Score 0
Fill in the blanks with the correct percentages of data contained within one, two, and three standard deviations of the mean in a normal distribution: ___%, ___%, ___%.
30
68%, 95%, 99.7%
50%, 90%, 98%
60%, 80%, 90%
75%, 85%, 95%
13 questions
Q.
Which of the following is a defining feature of a normal distribution?
1
30 sec
Q.
Fill in the blanks with the correct percentages of data contained within one, two, and three standard deviations of the mean in a normal distribution: ___%, ___%, ___%.
2
30 sec
Q.
TRUE or FALSE: In a standard normal distribution, the area to the right of z = 0 is 50%.
3
30 sec
Q.
Given a normal random variable X with mean μ = 100 and standard deviation σ = 20, convert X = 120 to its equivalent standard normal variable Z.
4
30 sec
Q.
Calculate the Z-scores for the following values: X = 90, 110, and 130, given μ = 100 and σ = 10.
5
30 sec
Q.
The company plans to improve quality by reducing the standard deviation from 40 hours to 25 hours. How does this change affect the probability of batteries lasting between 560 and 640 hours?
6
30 sec
Q.
Which of the following is a characteristic of a normal random variable?
7
30 sec
Q.
List the percentages of data contained within one, two, and three standard deviations from the mean in a normal distribution. Fill in the blanks: ____%, ____%, ____%.
8
30 sec
Q.
TRUE or FALSE. The region under the normal curve to the left of z=0 corresponds to 50% of the total area. Answer: ________
9
30 sec
Q.
Given a normal random variable X with μ=50 and σ=10, convert X=60 to its equivalent standard normal variable Z. Answer: ________
10
30 sec
Q.
Calculate the Z-scores for the following values of X = 45, 55, and 65, given μ = 50 and σ = 5. Answers: _________, __________, __________.
11
30 sec
Q.
The company wants to improve the quality of its bulbs by reducing the standard deviation from 50 hours to 30 hours. Analyze how this change affects the probability of bulbs lasting between 750 and 850 hours.
12
30 sec
Q.
How does decreasing the standard deviation of a product's lifespan from 40 hours to 25 hours affect the probability of the product lasting within a specified range?
