Math Problem Statement
Suppose
60
%
of people like balloons.
In a random sample of 102 people what is the probability that between 58 and 63 of them like balloons?
More precisely, let X be the random variable that counts how many people in samples of size n = 102 like balloons. Find
P
(
58
≤
X
≤
63
)
.
Give your answer as a decimal number between 0 and 1, accurate to at least 4 decimal places (something like 0.1234). Put your answer in the answer box.
Solution
To solve this, we can model the number of people who like balloons as a binomial random variable. The binomial distribution is appropriate because each person is independent, and they can either like balloons (with probability ) or not like them (with probability ).
Given:
- (sample size),
- (probability a person likes balloons),
- We need to find , where is the number of people in the sample who like balloons.
Step 1: Approximate the Binomial Distribution with a Normal Distribution
For large , we can use the normal approximation to the binomial distribution, which is typically accurate when is large and is not too close to 0 or 1.
The parameters for the normal distribution approximation are:
- Mean
- Standard deviation
Step 2: Apply the Continuity Correction
Since we're using a continuous distribution (normal) to approximate a discrete one (binomial), we apply a continuity correction by adjusting the values for the desired range:
- For , we use (i.e., ).
- For , we use (i.e., ).
Thus, we need to compute .
Step 3: Convert to Standard Normal Distribution (Z-Scores)
We convert these values into standard normal -scores using the formula:
For :
For :
Step 4: Use the Standard Normal Distribution Table or a Calculator
Now, we use the standard normal table or a calculator to find the cumulative probabilities corresponding to these -scores.
Step 5: Calculate the Desired Probability
The probability that is between 58 and 63 is the difference between these cumulative probabilities:
Final Answer:
The probability that between 58 and 63 people like balloons is approximately 0.4496.
Would you like further details or explanations on any part of this? Here are a few related questions:
- How do we calculate the mean and standard deviation for a binomial distribution?
- Why is the continuity correction necessary in normal approximation?
- What are the conditions for using the normal approximation to the binomial distribution?
- How do we use the Z-score to find probabilities in a normal distribution?
- Can this problem be solved directly using the binomial distribution instead of normal approximation?
Tip: When using the normal approximation, check that and are both greater than 5 to ensure the approximation is valid.
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Math Problem Analysis
Mathematical Concepts
Binomial Distribution
Normal Approximation to Binomial Distribution
Z-Scores
Probability Theory
Formulas
P(X ≤ x) = P(Z ≤ (x - μ) / σ)
μ = np
σ = sqrt(np(1-p))
Theorems
Central Limit Theorem
Normal Approximation to the Binomial Distribution
Suitable Grade Level
Grades 11-12
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