Math Problem Statement

The amount of calories consumed by customers at the Chinese buffet is normally distributed with mean 2762 and standard deviation 609. One randomly selected customer is observed to see how many calories X that customer consumes. Round all answers to 4 decimal places where possible.

a. What is the distribution of X? X ~ N(,)

b. Find the probability that the customer consumes less than 2425 calories. 

c. What proportion of the customers consume over 3039 calories? 

d. The Piggy award will given out to the 2% of customers who consume the most calories. What is the fewest number of calories a person must consume to receive the Piggy award?  calories. (Round to the nearest calorie)

Solution

Let's solve each part step-by-step using the information provided:

Given Data:

  • Mean (μ\mu) = 2762
  • Standard Deviation (σ\sigma) = 609

Part (a): Distribution of XX

Since the amount of calories consumed by customers follows a normal distribution: XN(2762,6092)X \sim N(2762, 609^2) Thus, XX is normally distributed with mean 2762 and variance 6092609^2.


Part (b): Probability that the customer consumes less than 2425 calories

To find P(X<2425)P(X < 2425):

  1. Calculate the z-score: z=Xμσ=24252762609=0.5534z = \frac{X - \mu}{\sigma} = \frac{2425 - 2762}{609} = -0.5534
  2. Use the z-score to find the probability from the standard normal distribution table: P(X<2425)=P(Z<0.5534)0.2894P(X < 2425) = P(Z < -0.5534) \approx 0.2894

So, the probability that a customer consumes less than 2425 calories is approximately 0.2894.


Part (c): Proportion of customers consuming over 3039 calories

To find P(X>3039)P(X > 3039):

  1. Calculate the z-score: z=30392762609=0.4557z = \frac{3039 - 2762}{609} = 0.4557
  2. Use the z-score to find the probability from the standard normal distribution table: P(X>3039)=1P(Z<0.4557)10.6756=0.3244P(X > 3039) = 1 - P(Z < 0.4557) \approx 1 - 0.6756 = 0.3244

So, the proportion of customers consuming over 3039 calories is approximately 0.3244.


Part (d): Fewest calories to receive the Piggy award (top 2% of customers)

To find the calories that correspond to the top 2%, we need to find the z-score associated with the 98th percentile (since top 2% are the highest values):

  1. The z-score for the 98th percentile is approximately 2.0537.
  2. Convert the z-score back to the original calorie scale: X=μ+zσ=2762+(2.0537)(609)=4011.24X = \mu + z \cdot \sigma = 2762 + (2.0537)(609) = 4011.24

Rounding to the nearest calorie, the fewest calories a person must consume to receive the Piggy award is 4011 calories.


Summary of Answers:

  • (a) XN(2762,6092)X \sim N(2762, 609^2)
  • (b) Probability that the customer consumes less than 2425 calories: 0.2894
  • (c) Proportion of customers consuming over 3039 calories: 0.3244
  • (d) Fewest calories for the Piggy award: 4011 calories

Would you like further explanation on any part of this solution?


Related Questions:

  1. What is the probability that a customer consumes between 2500 and 3000 calories?
  2. How would the answers change if the mean calorie consumption increased to 2800?
  3. What is the z-score of a customer consuming exactly 2762 calories?
  4. If the standard deviation decreased to 500, how would that affect the distribution of XX?
  5. What percentage of customers consume between 2200 and 3200 calories?

Tip:

To quickly estimate probabilities for normal distributions, remember that approximately 68% of data falls within one standard deviation of the mean, 95% within two, and 99.7% within three.

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Math Problem Analysis

Mathematical Concepts

Normal Distribution
Probability
Z-Scores
Percentiles

Formulas

z = (X - μ) / σ
Probability from the standard normal distribution table
X = μ + z * σ

Theorems

Empirical Rule for Normal Distribution
Properties of the Standard Normal Distribution

Suitable Grade Level

Grades 11-12