Skip to main content
Ch. 6 - Normal Probability Distributions
Triola - Elementary Statistics 14th Edition
Triola14th EditionElementary StatisticsISBN: 9780137366446Not the one you use?Change textbook
Chapter 6, Problem 6.5.21a

Transformations The heights (in inches) of women listed in Data Set 1 “Body Data” in Appendix B have a distribution that is approximately normal, so it appears that those heights are from a normally distributed population.


a. If 2 inches is added to each height, are the new heights also normally distributed?

Verified step by step guidance
1
Understand the concept of a normal distribution: A normal distribution is a symmetric, bell-shaped curve where most of the data points cluster around the mean, and the probabilities taper off as you move further from the mean.
Recognize the effect of adding a constant to a dataset: Adding a constant value (e.g., 2 inches) to every data point in a dataset shifts the entire distribution by that constant amount without changing its shape.
Recall that the shape of a normal distribution is determined by its mean and standard deviation. Adding a constant affects the mean (it increases by the constant) but does not affect the standard deviation or the overall shape of the distribution.
Conclude that if the original dataset is normally distributed, adding a constant to each value will result in a new dataset that is also normally distributed, as the shape of the distribution remains unchanged.
Verify the reasoning by considering the properties of transformations: Shifting a dataset by a constant is a linear transformation, which preserves the normality of the distribution.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
3m
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Normal Distribution

A normal distribution is a probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean. It is characterized by its bell-shaped curve and is defined by two parameters: the mean (average) and the standard deviation (spread). Many natural phenomena, including human heights, tend to follow this distribution.
Recommended video:
Guided course
09:47
Finding Standard Normal Probabilities using z-Table

Transformation of Data

Transforming data involves applying a mathematical operation to each data point in a dataset. In this case, adding a constant (2 inches) to each height shifts the entire distribution without altering its shape. This means that while the mean height increases, the overall distribution remains normal, preserving its properties.
Recommended video:
Guided course
04:39
Visualizing Qualitative vs. Quantitative Data

Properties of Normal Distribution under Transformation

One key property of normal distributions is that they remain normal under linear transformations, which include adding or subtracting a constant. This means that if you add a constant to a normally distributed variable, the result is still normally distributed, with the mean adjusted by the constant but the standard deviation unchanged.
Recommended video:
06:23
Using the Normal Distribution to Approximate Binomial Probabilities
Related Practice
Textbook Question

Ergonomics. Exercises 9–16 involve applications to ergonomics, as described in the Chapter Problem.


Aircraft Cockpit The overhead panel in an aircraft cockpit typically includes controls for such features as landing lights, fuel booster pumps, and oxygen. It is important for pilots to be able to reach those overhead controls while sitting. Seated adult males have overhead grip reaches that are normally distributed with a mean of 51.6 in. and a standard deviation of 2.2 in.


a. If an aircraft is designed for pilots with an overhead grip reach of 53 in., what percentage of adult males would not be able to reach the overhead controls? Is that percentage too high?

110
views
Textbook Question

Using the Central Limit Theorem. In Exercises 5–8, assume that the amounts of weight that male college students gain during their freshman year are normally distributed with a mean of 1.2 kg and a standard deviation of 4.9 kg (based on Data Set 13 “Freshman 15” in Appendix B).


a. If 1 male college student is randomly selected, find the probability that he gains between 0.5 kg and 2.5 kg during freshman year.

183
views
Textbook Question

Ergonomics. Exercises 9–16 involve applications to ergonomics, as described in the Chapter Problem.


Safe Loading of Elevators The elevator in the car rental building at San Francisco International Airport has a placard stating that the maximum capacity is “4000 lb—27 passengers.” Because 4000/27=148, this converts to a mean passenger weight of 148 lb when the elevator is full. We will assume a worst-case scenario in which the elevator is filled with 27 adult males. Based on Data Set 1 “Body Data” in Appendix B, assume that adult males have weights that are normally distributed with a mean of 189 lb and a standard deviation of 39 lb.


a. Find the probability that 1 randomly selected adult male has a weight greater than 148 lb.

101
views
Textbook Question

Using the Central Limit Theorem. In Exercises 5–8, assume that the amounts of weight that male college students gain during their freshman year are normally distributed with a mean of 1.2 kg and a standard deviation of 4.9 kg (based on Data Set 13 “Freshman 15” in Appendix B).

a. If 1 male college student is randomly selected, find the probability that he gains between 0 kg and 3 kg during freshman year.

149
views
Textbook Question

Using the Central Limit Theorem. In Exercises 5–8, assume that the amounts of weight that male college students gain during their freshman year are normally distributed with a mean of 1.2 kg and a standard deviation of 4.9 kg (based on Data Set 13 “Freshman 15” in Appendix B).


a. If 1 male college student is randomly selected, find the probability that he has no weight gain during his freshman year. (That is, find the probability that during his freshman year, his weight gain is less than or equal to 0 kg.)

146
views
Textbook Question

Mendelian Genetics When Mendel conducted his famous genetics experiments with peas, one sample of offspring consisted of 929 peas, with 705 of them having red flowers. If we assume, as Mendel did, that under these circumstances, there is a 3/4 probability that a pea will have a red flower, we would expect that 696.75 (or about 697) of the peas would have red flowers, so the result of 705 peas with red flowers is more than expected.


a. If Mendel’s assumed probability is correct, find the probability of getting 705 or more peas with red flowers.

147
views