ch11 - 1 Ch 11 Chance Errors in Sampling A health study is...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 1 Ch 11 Chance Errors in Sampling A health study is done on a representative cross section of 4,738 adults The researcher can sample only 100 of them Our question is whether the sample is representative? Assume the population had 3,032 (64%) male Then we might pick F F M F M F F M F M M F M M M M F M M M M F M F M M F M F M M M F F M M M F F M M M M F M M M M F M M F M M F M F M M F M F M M M M F M M M M M M M F M M M M F M F M M F M F M M F M M F M M M M F M M F F F M M F F F M M M F M M F M F M M F F M M F M F M M F M M F M M F M F M M F M F M M M M F M M M F F M F F F F M F F M F M F M M F M F M F F M M F F F M M F M M M M F M M M M F M M M F M M M M F M ( M=63, F=37) 2 Repeat i ng t hi s 250 t i mes Repeat i ng t hi s 250 t i mes 63 59 64 70 71 66 71 61 65 65 74 65 62 68 65 69 74 65 62 62 59 59 64 68 57 67 60 60 60 65 65 58 72 66 65 66 65 68 68 63 57 59 61 63 67 63 55 61 69 69 59 60 64 66 59 65 67 63 56 58 61 67 63 61 65 61 62 65 64 69 67 65 65 68 66 59 65 62 63 67 68 51 63 62 68 65 69 63 59 61 68 69 75 67 65 62 63 60 65 67 64 71 66 65 60 65 64 65 68 59 66 71 64 66 57 59 60 61 61 61 63 60 70 73 66 66 70 66 67 63 63 60 60 56 62 68 71 64 66 57 58 66 66 62 73 70 62 60 64 72 66 65 72 63 62 66 61 64 59 58 58 68 67 74 63 66 60 66 62 67 65 64 58 66 59 68 64 65 66 64 63 70 58 55 54 70 58 60 74 63 63 73 65 61 66 60 62 70 66 66 63 58 60 64 58 61 59 54 61 55 64 65 64 66 58 68 66 62 69 65 67 69 62 61 65 68 73 68 58 58 62 72 65 69 61 65 72 64 70 67 63 67 62 66 63 58 64 67 69 72 We got 64 onl y 18 t i mes We got 64 onl y 18 t i mes - pr obabi l i t y - pr obabi l i t y of get t i ng exact l y 64 mal es i n our sampl e of get t i ng exact l y 64 mal es i n our sampl e i s pr et t y l ow ( i . e. 18/ 250) i s pr et t y l ow ( i . e. 18/ 250) 3 The proportion of male in the population remains at 64%, but the proportion in the sample varies due to chance error . Below is a histogram of the number of men from the samples of size 100 persons (i.e. 250 repetitions) cf . Ker r i ch exper i ment ; Chance var i abi l i t y i n sampl i ng j ust l i ke chance var i abi l i t y i n coi n t ossi ng. 5 10 15 49 52 55 58 61 64 67 70 73 76 - % No. men 4 What if we increase the sample size from 100 to say 400? Following the LAW of AVERAGES, as sample size increases, chance error in percentage decreases. percentage in sample = percentage in population + chance error The bigger the sample, the closer the sample proportion to the population proportion....
View Full Document

This note was uploaded on 03/14/2010 for the course ECON Statistics taught by Professor Yy during the Spring '10 term at Seoul National.

Page1 / 27

ch11 - 1 Ch 11 Chance Errors in Sampling A health study is...

This preview shows document pages 1 - 5. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online