Suppose that a city has 90,000 dwelling units, of which 35,000 are houses, 45,000 are apartments, and 10,000 are condominiums. you believe that the mean electricity usage is about twice as much for houses as for apartments or condominiums, and that the standard deviation is proportional to the mean so that si = 2s2 = 2s3. how would you allocate a stratified sample of 900 observations if you wanted to estimate the mean electricity consumption for all households in the city? now suppose that you take a stratified random sample with proportional allocation and want to estimate the overall proportion of households in which energy conservation is practiced. if 45% of house dwellers, 25% of apartment dwellers, and 3% of condominium residents practice energy conservation, what is p for the population? what gain would the stratified sample with proportional allocation offer over an srs, that is, what is vprop(pstr)/vsrs(psrs)?

Give the equations of two different lines that are perpendicular to the line 3x + 4y = 7.

With this question substitute t=3 and t=5 to determine if the two expressions are equivalent. 4(t + 3) 4t+12 which statements are true? check all that apply. a. the value of both expressions when t =5 is 32. b. the two expressions are not equivalent. c. the value of both expressions when t=3 is 15. d. the value of both expressions when t=5 is 23. e. the two expressions are equivalent. f. the value of both expressions when t=3 is 24.

An annual marathon covers a route that has a distance of approximately 26 miles. winning times for this marathon are all over 2 hours. the following data are the minutes over 2 hours for the winning male runners over two periods of 20 years each. earlier period 14 12 15 22 13 10 19 13 9 14 20 18 16 20 23 12 18 17 6 13 recent period 7 11 7 14 8 9 11 14 8 7 9 8 7 9 9 9 9 8 10 8 (a) make a stem-and-leaf display for the minutes over 2 hours of the winning times for the earlier period. use two lines per stem. (use the tens digit as the stem and the ones digit as the leaf. enter none in any unused answer blanks. for more details, view how to split a stem.) minutes beyond 2 hours earlier period 0 1 2 (b) make a stem-and-leaf display for the minutes over 2 hours of the winning times for the recent period. use two lines per stem. (use the tens digit as the stem and the ones digit as the leaf. enter none in any unused answer blanks.) minutes beyond 2 hours recent period (c) compare the two distributions. how many times under 15 minutes are in each distribution