In: Statistics and Probability
Use the normal distribution to approximate the following binomial distribution. A soccer player has a 65% chance of making a free kick. What is the probability of him making fewer than 24 free kicks in 40 kicks?
a)0.2546
b)0.2119
c)0.2033
d)0.3085
e)0.1611
f) None of the above.
Answer:-
Given That:-
Use the normal distribution to approximate the following binomial distribution. A soccer player has a 65% chance of making a free kick. What is the probability of him making fewer than 24 free kicks in 40 kicks?
Given,
X ~ Binomial(n = 40, p = 0.65)
Binomial can be approximated to normal with
= 40 * 0.65
= 26
= 3.016621
3.017
P(X < 24)
Since we are approximating a discrete binomial distribution by continous normal distribution, values between 23.5 and 24.5 both approximation to 24. Thus "less than 24" corresponds to continuous normal distribution with X < 23.5 after continuity correction.
Normal Distribution x = 23.5
,
We convert this to standard normal using
P(X < 23.5) = Area to the left of 23.5
,
P(X < 23.5) = P(Z < -0.83)
= 0.2033 (from z - table)
P(X is less than 24) = 0.2033
If excel is used instead of z - table, it would be: 0.2036252560
Note that if this question is solved without continuity correction, the answer would have been:
P(X < 24) = P(Z < -0.66)
= 0.2546
Without integer - continuity correction:
P(X < 24) = 0.2546
If excel is used instead of z - table, it would be: 0.2536673707
The correct answer is option (a)
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