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These WINKS statistics tutorials explain the use and interpretation of standard statistical analysis techniques for Medical, Pharmaceutical, Clinical Trials, Marketing or Scientific Research. The examples include how-to instructions for WINKS SDA Version 6.0 Software. Download evaluation copy of WINKS.
Description of Options for
WINKS Crosstabulation Analysis (Chi-square)
Notes on 2x2 Table Statistics
Several other specialized statistics are provided for 2x2 tables. They do not apply to the previous example, but are typically used in a medical setting where the variables are often exposure to a disease (or some stimulus) versus the observation of some outcome – for example smoking vs cancer or exposure to a chemical vs pulmonary disease. When your data are in that setting, the risk statistics given by Relative Risk, Odds Ratio, Sensitivity and Specificity may be useful:
Note: Sensitivity and Specificity calculations are only available on the crosstabulations with data entered from the keyboard. Results are based on a table where the cells are in the following pattern:
TP | FP
————————
FN | TNWhere T=True, F=False, P=Positive, and N=Negative.
Specificity is a measure of the ability to call negative patients/subjects that do not have the disease or condition. For more information on these four statistics, reference any biostatistics or epidemiology text. One example is Basic Biostatistics in Medicine and Epidemiology, A. A. Rimm, Appleton-Century-Crofts, 1980.
Definition of Cell Options
- Frequency – Displays Observed frequencies for the table
- Expected - displays the expected cell frequencies under the hypothesis of independence (the value is calculated by multiplying marginal counts and dividing by the table total count.
- Contribution to Chi-Square - crosstabulation table individual cell’s contribution to the total Pearson chi-square statistic.
- Residual - (unstandardized residuals) displays the deviation of the frequency from the expected frequency for each cell of the crosstabulation table. That is (Observed-Expected)
- Standardized (or Studentized) Residuals - is calculated as
(Observed -Expected) / sqrt(Expected)
This value is an approximate standard normal value. Thus, when the standardized residual is greater than 2.00 (some will say 1.96), it indicates that this cell provides an important contribution to the overall significance of the table. - Adjusted Standardized Residuals (Haberman Residuals) – These residuals are similar to the standardized residuals, but is reported to be more accurate for making a decision of a cell's contribution to significance. (See Haberman, 1973, Biometrics Vl 29. No 1.) The formula for this value is
(Observed-Expected)/[sqrt(Expected)*sqrt(1-RowMarginal/N)sqrt(1-ColMarginal/N].
They are interpreted the same way as the standardized residuals.
These WINKS statistics tutorials briefly explain the use and interpretation of standard statistical analysis techniques for Medical, Pharmaceutical, Clinical Trials, Marketing or Scientific Research. The examples include how-to instructions for WINKS SDA Version 6.0 Software.
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