How to compare percentages scores

[AR-4]

How to compare  percentages scores.

Dear list:
    I'd like to know if there are significant differences between the
presence of two different a substances in blood.

We have detected the substance A in 986 people. 120 females out of 218
had it. 450 out of 768 males also had it. (768+218=986)
We have detected the substance B in 163 people. 7 females out of 27 had
it. 45 out of 136 males also had it. (27+136=163)

I know I can perform a chi-2 test to know if sex depend on each
substance presence (ns), but how can I do find differs between the
substances?.

Any help will be appreciated.

[Melissa Ives]

We have a power analysis worksheet available for download on our website
that should allow you to calculate the effect size for this.

http://www.chestnut.org/LI/downloads/index.html
Click on Research Tools and select the first one "Power Analysis
Worksheet" (see a copy of the blurb below).

Research Tools

Author: Michael Dennis, Ph.D., Richard I. Lennox, Ph.D., Mark Foss,
Ph.D.
Name: Power Analysis Worksheet

Description: This document contains a spread sheet for calculating
effect sizes based on percentage point differences, a
R-square/Eta-square, a chi-square, or means and standard deviations. For
more information on the formulas or power analysis see Dennis, M.L.,
Lennox, R.I., & Foss, M. (1997). Practical power analysis for substance
abuse health services research. In Bryant, K., Windle, M., & West,
S.,G.(eds.), The science of prevention: Methodological advances from
alcohol and substance abuse research, (pp 367-404). Washington, DC:
American Psychological Association.

Date: August 29, 1997
File Name: eswk.xls
File Version: 8/97
File Format: Microsoft Excel 7.0
File Size: 26 K

Melissa

-----Original Message-----
From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of
AR
Sent: Wednesday, September 27, 2006 5:45 AM
To: [hidden email]
Subject: [SPSSX-L] How to compare percentages scores

How to compare  percentages scores.

Dear list:
    I'd like to know if there are significant differences between the
presence of two different a substances in blood.

We have detected the substance A in 986 people. 120 females out of 218
had it. 450 out of 768 males also had it. (768+218=986) We have detected
the substance B in 163 people. 7 females out of 27 had it. 45 out of 136
males also had it. (27+136=163)

I know I can perform a chi-2 test to know if sex depend on each
substance presence (ns), but how can I do find differs between the
substances?.

Any help will be appreciated.



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