PSY3204C Chapter 6 Quiz

For a normal distribution with μ = 2 and σ = 0.5, what is p(X < 1.7) + p(X < 2.3)?

1

Which z-score mark separates the bottom 97.5% from the top 2.5% in a normal distribution?

1.96

If a multiple choice quiz has 100 questions in which every question has 4 choices, what is the probability of getting fewer than 20 questions correct merely by guessing?

10%

The population distribution of scores on a test is normal with μ = 40 and σ = 2. What is the probability of scoring less than a 38 on this test?

15.87%

A population of insect weights is normal with a mean of μ = 16. If the probability of a weight falling between 10 and 22 is 95.44%, what is the standard deviation for this distribution?

3

Which of the following is not a valid probability?

6/5

A population of plant heights has a mean of μ = 13 and standard deviation of σ = 2. What is the probability of an individual plant having a height between 10 and 16?

86.64%

Which of the following is equal to p(z > 2.00) in a normal distribution? I. p(z < -2.00) II. 1 - p(z < 2.00) III. ½ p(z > 1.00)

I and II only

There are five cards face down on a table with the values 1, 2, 3, 4, and 5 written on them. James says that the probability of randomly turning over an even number is ½ because there are two possibilities: even and odd. Which of the following statements is true?

James is incorrect because the two possibilities of "even" and "odd" are not equally likely in this situation.

A population of birth weights has a mean of μ = 8.1, and a standard deviation of σ = 0.1. What is the probability of an individual weight being greater than 8.4?

0.13%

There are 12 blue marbles, 8 red marbles, and 20 green marbles in a jar. A marbles is drawn from the jar and replaced. This is repeated 4 times, and each time a green marble is drawn. On the fifth time, what is the probability of drawing a green marble?

0.5

The number of minutes spent reading in one day is normally distributed with a mean of μ = 23 and a standard deviation of σ = 5. How much time would you have to spend reading in a day to find yourself in the top 10% of readers?

29.4

What is the probability of a z-score falling within one standard deviation of the mean in a normal distribution?

68.26%

What is the best explanation for why a normal distribution is only an approximation for a binomial distribution?

Binomial values are discrete, and normal values are continuous

The wingspan of a population of insects is normally distributed with μ = 42 and σ = 4. Which of the following is true? I. It is possible for an insect in this population to have a wingspan of 30. II. It is likely for an insect in this population to have a wingspan of 30. III. It is unlikely an insect in this population to have a wingspan of 30.

I and II only

Which of the following is a proper way to describe the probability of flipping heads on a fair coin?

I, II, and III

What is the probability of a z-score being less than 2 standard deviations from the mean in a normal distribution?

More than 95%

Given that p = 0.5, for which value of n will the bar graph for the corresponding binomial distribution look most like a normal distribution?

N=100

For a normal distribution with a mean of 60 and a standard deviation of 5, what X values separate the middle 95% from the extreme values?

X = 50.2 and X = 69.8

For a binomial distribution with p = 0.75 and n = 15, the probability of A occurring more than 10 times is about 68.65%. Using a normal distribution with μ = 11.25, σ = 1.667, and p(X >10.5) to approximate this probability gives 67.26%. Which of the following best explains the discrepancy between the actual value of 68.65% and the approximation of 67.26%?

nq is not high enough to achieve a closer approximation