An allergy medication is successful in treating 60% of all patients who use it. The medication is given to 200 patients. Let X

In statistics, a normal distribution's probability density function is represented by a symmetrical bell-shaped curve. The likelihood that the random variable will fall between two values that define a vertical portion of the curve is represented by the area of the section.

According to the question,

An allergy medication is successful in treating 70%

The medication is given to 200 patients.

Thus,

The random variable X is a binomial random variable with n = 200 (there were 200 patients).

The probability that a medication is successful in treating a randomly selected patient is 0.7.

p = 0.7 (the medication was successful in 70% cases).

Step 1: Use the formulas for mean and standard deviation of a binomial random variable X.

[tex]\begin{gathered}\mu=E(X)=n \cdot p \\\sigma=\sqrt{n \cdot p \cdot(1-p)}\end{gathered}[/tex]

Substitute values of 'n' and 'p' to get the result,

[tex]\begin{gathered}\mu=200 \cdot 0.7=140 \\\sigma=\sqrt{200 \cdot 0.7 \cdot 0.3}=\sqrt{42}=6.4807 .\end{gathered}[/tex]

Thus, the mean is obtained as 140.

The standard deviation is 6.4807.

Step 2: find P(X≤128)

As a result, the prerequisites for a normal approximation to the binomial distribution are satisfied.

[tex]$n \cdot p=200 \cdot 0.7=140 \geq 10$$n \cdot(1-p)=200 \cdot 0.3=60 \geq 10 .$[/tex]

[tex]\begin{aligned}P(X \leq 128) & \approx P\left(Z \leq \frac{128-n \cdot p}{\sqrt{n \cdot p \cdot(1-p)}}\right)=P\left(Z \leq \frac{128-200 \cdot 0.7}{\sqrt{200 \cdot 0.7 \cdot(1-0.7)}}\right) \\&=P(Z \leq-1.85)=0.0322\end{aligned}[/tex]

Therefore, the probability that X is 128 or less. is 0.0322.

To know more about the normal distribution, here

https://brainly.com/question/23418254

#SPJ4

The complete question is-

An allergy medication is successful in treating 70% of all patients who use it. The medication is given to 200 patients. Let X = number of successful treatments. What are the mean and standard deviation of X? Use the normal curve to approximate the probability that X is 128 or less.