Please provide a step by step solution and be detailed. Your handwriting should

Question

Please provide a step by step solution and be detailed. Your handwriting should also be redabale.

4 points) The time in hours for a worker to repair an electrical instrument is a Normally distributed random variable with a mean of and a standard deviation of 50. The repair times for 12 such instruments chosen at random are as follows: 183 222 303 262 178 232 268 201 244 183 201 140 Part a) Find a 95% confidence interval for . For both sides of the bound, leave your answer with 1 decimal place. ( Part b) Find the least number of repair times needed to be sampled in order to reduce the width of the confidence interval to below 30 hours.

Explanation / Answer

here estimated mean =218.0833

for std error of mean =std deviation/(n)1/2 =50/(12)1/2 =14.4338

for 95% CI ; critical value of z =1.96

therfore 95% confidence interval =sample mean -/+ z*std error =189.8 ; 246.4

b)

for margin of error E =30/2=15

therfore sample size requried n=(z*std deviation/E)2 =~43

Related Questions

Navigate

• Browse (All)
• Browse P
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.