1. 80% of the children spend at least how long per day unsupervised? 2. C. How l

Question

1. 80% of the children spend at least how long per day unsupervised? 2. C. How long do the longest 20% of pregnancies last D. What are the quartile of the distribution of lengths of human pregnancies Suppose 4-year-olds in a certain country average 3 hours a day unsupervised and that most of the unsupervised children live in rural areas, considered safe. Suppose that the standard deviation is 1.8 hours and the amount of time spent alone is normally distributed. We randomly survey one 4-year-old living in a rural area. We are interested in th amount of time the child spends alone per day. Part (a) Part (b) Part (c) Part (d) of the children spend at least how long per day unsupervised? (Round your answer to two decimal places.) 2 The length of human pregnancies from conception to bith vanies according to a distribution that is approximately Normal with mean 259 days and standard deviation 20 days (a) What proportion of pregnancies last less than 270 days (about 9 months)? 708a / (Use 4 decimal places) (b) What proportion of pregnancies last between 240 and 270 days (roughly between 8 months and 9 months)? [5378(Use 4 decimal places) (c) How long do the longest 20% of pregnancies last? x (Use 2 decimal places) (d) What are the quartles of the distribution of lengths of human pregnancies? (Use 2 decimal places)

Explanation / Answer

1) Z = (x )/ for normal distribution

Here, = standard deviation = 1.8 hrs

= mean = 3 hrs

Z value corresponsing to 80% is 1.28 (Use Z value table to get Z value corresponsing to (1 0.8)/2 )

Thus, 1.28 = (x 3)/ 1.8

x = 5.304 hrs

So, 80% children spend at least 5.304 hrs per day unsupervised

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