Statistics Chapter 7 Quiz

Answer: Mean =97 and Std. Dev = 9

Question see graph in picture

Answer: The graph cannot represent a normal density because it is not symmetric

Question see picture

Find the area under the standard normal curve to the right of z= -1.25

The answer is 0.8944. To see how it is solved look at the results of the normal calculator below

For a standard normal curve, find the z-score that separates the bottom 90% from the top 10%

1.28 See picture on how to solve on Normal Calculator. When you do it make sure P(X < _____________ =.90

Find the z-score for which the area under the standard normal curve to the left is 0.96

1.75 See how it was solved on normal calculator.

The length of time it takes college students to find a parking lot follows a normal deviation with a mean of 4.5 minutes and a standard deviation of 1 minute. Find the probability that a randomly selected college student will take between 3 and 5.5 minutes to find a parking spot in the library lot.

0.7745

Approximately​ ____% of the area under the normal curve is between μ -2σ and μ + 2σ.

95% See Empirical Rule in picture below

Find the value of za. z0.16

Answer 0.99. To solve take 1-0.16=.84 then go to normal calculator. P(x<__________=.84

Suppose a brewery has a filling machine that fills 12 ounce bottles of beer. It is known that the amount of beer poured by this filling machine follows a normal distribution with a mean of 12.18 ounces and a standard deviation of 0.04 ounce. Find the probability that the bottle contains fewer than 12.08 ounces of beer.

Answer 0.9938 Go to Normal Calculator. See picture

Determine the two z-scores that separate the middle 87.4% of the distribution from the area in the tails of the standard normal distribution.

Answer: -1.53, 1.53 See how it is solved in the picture below. Go to normal calculator between P<__________<=.874 compute

Assume that the random variable X is normally distributed with mean = 80 and Standard deviation = 5. Compute the probability P(x>84).

Answer: 0.2119 To solve use normal calculator. See results in the picture below.

Determine the area under the standard normal curve that lies between the following values. z=0.5 and z=1.4

Answer: 0.2277

Find the area under the standard normal curve to the left of z=1.25

Answer: 0.8944 Go to normal calculator. See how it is solved in the picture below

Assume the random variable X is normally distributed, with mean = 40 and standard deviation = 8. Compute the probability P(X<50)

Answer: 0.8944 To solve use normal calculator. See results in the picture below

A physical fitness association is including the mile run in its secondary-school fitness test. The time for this event for boys in secondary school is known to possess a normal distribution with a mean of 450 seconds and a standard deviation of 50 seconds. Find the probability that a randomly selected boy in secondary school will take longer than 335 seconds to run the mile.

Answer: 0.9893 To solve go to normal calculator. See picture of graph

Find the z-score for which the area under the standard normal curve to its right is 0.07

Answer: 148 To see how it is solved look at the results of the normal calculator below

Approximately___________% of the area under the normal curve is between μ -σ and μ + σ.

Answer: 68 The Empirical Rule: Approximately 68% of the area under the normal curve is between μ -σ and μ + σ. See Empirical Rule below

The normal probability plot does indicates that the sample data could have come from a population that is normally distributed.

Determine whether the accompanying normal probability plot indicates that the sample data could have come from a population that is normal

The normal probability plot does not indicate that the sample data could have come from a population that is normally distributed.

Determine whether the following normal probability plot indicates that the sample data could have come from a population that is normally distributed.

What is the normal density curve symmetric about?

It's mean