The probability that fewer than 22 customers in the sample buy coffee during their visit is 0.7764.
What is a normal approximation to the binomial?
When we utilize a continuous distribution (the normal distribution) to approximate a discrete distribution, we use the normal approximation to the binomial (the binomial distribution). The Central Limit Theorem states that if the sample size is high enough, the sampling distribution of the sample means approximates normality.
In a normal distribution with mean and standard deviation, the z-score of a measure X is given by:
[tex]Z=\frac{X-\mu}{\sigma}[/tex]
Given, 55% of the customers buy coffee, p = 0.55
Sample of 35 customers, n = 35
mean [tex]\mu[/tex] = np = 35*0.55 = 19.25
standard deviation, [tex]\sigma = \sqrt{np(1-p)}[/tex] = [tex]\sqrt{35*0.55*0.45}[/tex] = 2.94
So, the probability that fewer than 23 customers in the sample buy coffee is
P(X < 22 - 0.5) = P(X < 21.5)
= [tex]P(\frac{X-\mu}{\sigma} < \frac{21.5-19.25}{2.94})[/tex]
= P(Z<0.765) = 0.7764
Hence, the probability that fewer than 22 customers in the sample buy coffee during their visit is 0.7764.
To learn more about a normal approximation to the binomial
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