An investment website can tell what devices are used to acc

) An investment website can tell what devices are used to access the site. The site managers wonder whether they should enhance the facilities for trading via \"smartphones\" so they want to estimate the proportion of users who access the site that way. They draw a random sample of 200 investors from their customers. Suppose that the true proportion of smart phone users is 36%.

a) What would the standard error of the sampling distribution of the proportion of smart phone users be?

b) What is the probability that the sample proportion of smart phone users is greater than 0.36?

c) What is the probability that sample proportion is between 0.30 and 0.40?

d) What is the probability that the sample proportion is less than 0.28?

e) What is the probability that the sample proportion is greater than 0.42?

2) From a survey of 250 coworkers you find that 155 would like the company to provide on-site day care.

f) what is the standard error of the sample proportion?

g) construct an approximate 95% confidence interval for the true proportion p by taking +/- 2 SEs from the sample proportion

3) Identify which type of sampling is used. Explain.

During a quality inspection for correct UPC of chewing gum, all of the packages at the checkout counter rack were checked.

h) cluster

i) convenience

j) random

k) stratified

l) systematic

4) The police chiefs of ten towns in the county were asked if tickets issued by red light cameras were fair. Is this an example of convenience, judgment, or probability sampling? Explain.

4) For a population N = 902, use the random number table E1 beginning at row 05, column 01 to find a sample size of 30 (n = 30). How many rows will be needed? What will be last value selected?

Solution

n 200 p 36% 0.36 Std error rt of{ p(1-p)/n} 0.0339 p is normal with (0.36, 0.0339) b) P(p>0.36) P(Z>0) 0.5 c) P(0.30.42) P(Z>1.77) 0.0384 0.000942 0.030699 2) p 0.62 f) Std error 0.0307 CE 0.5586 0.6814