As part of the safety propotocol, an asbestos removal company is interested in k

Question

As part of the safety propotocol, an asbestos removal company is interested in knowing if any asbestos particles left on the employee’s skin after a day's work wearing the protective suit. A random sample of 150 employees had skin tests after removing their protective suits. The average number of particles found was .471 particles per square centimeter. Assuming that the population standard deviation is 0.38 particles per square centimeter, calculate a 95% confidence interval for the number of particles left on the employee’s skin.

Explanation / Answer

Confidence Interval
CI = x ± Z a/2 * (sd/ Sqrt(n))
Where,
x = Mean
sd = Standard Deviation
a = 1 - (Confidence Level/100)
Za/2 = Z-table value
CI = Confidence Interval
Mean(x)=0.471
Standard deviation( sd )=0.38
Sample Size(n)=150
Confidence Interval = [ 0.471 ± Z a/2 ( 0.38/ Sqrt ( 150) ) ]
= [ 0.471 - 1.96 * (0.031) , 0.471 + 1.96 * (0.031) ]
= [ 0.41,0.532 ]

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