Math Problem Statement
Assume that women's weights are normally distributed with a mean given by 143 lb and a standard deviation given by 29 lb. (a) If 1 woman is randomly selected, find the probabity that her weight is between 108 lb and 179 lb
(b) If 6 women are randomly selected, find the probability that they have a mean weight between 108 lb and 179 lb
(c) If 95 women are randomly selected, find the probability that they have a mean weight between 108lb and 179 lb
Solution
We are dealing with a normally distributed population of women’s weights with a mean and a standard deviation . To solve the given questions, we will use Z-scores and the properties of the standard normal distribution.
Part (a):
If 1 woman is randomly selected, find the probability that her weight is between 108 lb and 179 lb.
We convert both bounds (108 lb and 179 lb) into Z-scores using:
For 108 lb:
For 179 lb:
Using standard normal distribution tables or a calculator:
Now, the probability that the woman's weight is between 108 and 179 lb:
So, the probability is:
Part (b):
If 6 women are randomly selected, find the probability that they have a mean weight between 108 lb and 179 lb.
When dealing with the sample mean, the standard deviation becomes:
Here, , so:
Now, we recalculate the Z-scores with the new standard deviation:
For 108 lb:
For 179 lb:
Using standard normal distribution tables:
Now, the probability that the mean weight is between 108 and 179 lb:
So, the probability is:
Part (c):
If 95 women are randomly selected, find the probability that they have a mean weight between 108 lb and 179 lb.
For this larger sample size , the standard deviation of the sample mean becomes:
Now, we recalculate the Z-scores:
For 108 lb:
For 179 lb:
Using the standard normal table:
- is extremely close to 0.
- is extremely close to 1.
Thus, the probability that the mean weight is between 108 and 179 lb:
So, the probability is:
Summary of Results:
- (a) Probability for 1 woman:
- (b) Probability for 6 women:
- (c) Probability for 95 women:
Do you need further clarification or more details?
Here are 5 related questions:
- What is the probability that a randomly selected woman weighs more than 200 lb?
- How does increasing the sample size affect the standard deviation of the sample mean?
- What is the Z-score corresponding to a weight of 143 lb?
- How would the probabilities change if the standard deviation were smaller?
- What is the meaning of the central limit theorem in the context of these problems?
Tip: As the sample size increases, the variability of the sample mean decreases, leading to probabilities closer to 1 for values near the population mean.
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Math Problem Analysis
Mathematical Concepts
Normal Distribution
Z-Scores
Probability
Sampling Distribution
Formulas
Z = (X - μ) / σ
σₓ̄ = σ / √n
P(Z < z)
Theorems
Central Limit Theorem
Suitable Grade Level
Grades 11-12 or Introductory College Level
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