7) The interval (7, 11) is a 80% confidence interval. Calculate the standard dev

Question

7) The interval (7, 11) is a 80% confidence interval. Calculate the standard deviation.(hint: calculate the error, look at the table middle for 80% probability and the solve error-Zs) a) 0.1 b) 1.56 c) 1.2 d) 1 e) None For the last 25 days I recorded the number of times people knock at my door. The Maximum was 19 and the minimum 11 and the average was 15 times per day, build a 95% confidence interval. 8) a) (11,23) b) (15.16,17.51) c) (15.1,17.6) d) (14.2,15.8) e) None For a normally distributed random variable with average 1000 and standard deviation 100 a 68% confidence interval will look like this a) (1000,1100) b) (900,2100) c) 68% d) (900, 1100) e) None 9)

Explanation / Answer

Ans:

7)Margin of error=(11-7)/2=4/2=2

z value for 80% CI is 1.28

2=1.28*standard deviation

standard deviation=2/1.28=1.56

Option b is correct.

8)

Range=19-11=8

standard deviation=8/4=2

z value for 95% CI is 1.96

95% CI =15+/-1.96*2/sqrt(25)

=15+/-0.8

=(14.2,15.8)

Option d is correct.

9)z value for 68% CI is 1

68% CI=1000+/-1*100

(900,1100)

Option d is correct.

Related Questions

Navigate

• Browse (All)
• Browse 7
• Subjects

---

---

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