Math Problem Statement

The amount of calories consumed by customers at the Chinese buffet is normally distributed with mean 2659 and standard deviation 512. 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? b. Find the probability that the customer consumes less than 2489 calories. c. What proportion of the customers consume over 2802 calories? d. The Piggy award will be 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?

Solution

Let's go through the questions based on the provided information:

We are told that the amount of calories consumed by customers at the buffet is normally distributed with:

  • Mean μ=2659\mu = 2659 calories
  • Standard deviation σ=512\sigma = 512 calories

The problem asks us to work with the normal distribution XN(μ,σ2)X \sim N(\mu, \sigma^2), where XX represents the calories consumed by a randomly selected customer.

Part (a): Distribution of XX

The distribution of XX is given as a normal distribution with the provided mean and standard deviation. XN(2659,5122)X \sim N(2659, 512^2) So, for part (a), the answer is: XN(2659,5122)X \sim N(2659, 512^2)

Part (b): Probability that the customer consumes less than 2489 calories

We need to find P(X<2489)P(X < 2489). First, we compute the z-score: z=Xμσ=24892659512=1705120.3320z = \frac{X - \mu}{\sigma} = \frac{2489 - 2659}{512} = \frac{-170}{512} \approx -0.3320 Next, we look up the z-score of 0.3320-0.3320 in the standard normal distribution table (or use a calculator). The corresponding probability is approximately: P(Z<0.3320)0.3707P(Z < -0.3320) \approx 0.3707 So, the probability that the customer consumes less than 2489 calories is approximately 0.37070.3707.

Part (c): Proportion of customers consuming more than 2802 calories

Here, we calculate P(X>2802)P(X > 2802). First, compute the z-score: z=28022659512=1435120.2793z = \frac{2802 - 2659}{512} = \frac{143}{512} \approx 0.2793 Using the z-score table or a calculator, P(Z<0.2793)0.6099P(Z < 0.2793) \approx 0.6099. Since we want the proportion consuming more than 2802 calories, we compute: P(X>2802)=1P(Z<0.2793)=10.6099=0.3901P(X > 2802) = 1 - P(Z < 0.2793) = 1 - 0.6099 = 0.3901 Thus, the proportion of customers consuming more than 2802 calories is approximately 0.39010.3901.

Part (d): Piggy award (top 2%)

The Piggy award goes to the top 2% of customers. This means we need to find the calorie amount that corresponds to the 98th percentile of the normal distribution.

Looking up the z-score corresponding to the 98th percentile, we find: P(Z<z)=0.98z2.054P(Z < z) = 0.98 \quad \Rightarrow \quad z \approx 2.054 Now, we solve for the calorie threshold using the z-score formula: X=μ+zσ=2659+2.054×5122659+1051.65=3711.65X = \mu + z \sigma = 2659 + 2.054 \times 512 \approx 2659 + 1051.65 = 3711.65 Rounding to the nearest calorie, the fewest number of calories a person must consume to receive the Piggy award is approximately 37123712 calories.


Would you like further details or clarifications? Here are five related questions that expand on the concepts:

  1. What is the probability that a customer consumes between 2489 and 2802 calories?
  2. If the mean changes to 2700 calories, how would the answers to parts (b) and (c) change?
  3. How would the proportion in part (c) change if the standard deviation increased to 600?
  4. Can you find the 90th percentile of the calorie distribution?
  5. What is the probability that a customer consumes more than 3500 calories?

Tip: When working with normal distributions, z-scores allow you to standardize any value and use the standard normal table to find probabilities or percentiles.

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Math Problem Analysis

Mathematical Concepts

Probability
Normal Distribution
Z-Score
Percentiles

Formulas

z = (X - μ) / σ
P(X < X_value) from z-tables
P(X > X_value) = 1 - P(X < X_value)
X = μ + z * σ

Theorems

Normal Distribution Theorem
Z-Score and Percentile Calculation

Suitable Grade Level

Grades 11-12 (Advanced High School, College Level)