IHStat is a statistical software package developed by the American Industrial Hygiene Association to evaluate occupational samples. It computes descriptive statistics, determines if data is normally or log-normally distributed, and calculates confidence limits. The software guides the user through entering exposure limit, clearing existing data, inputting sample data, and obtaining descriptive statistics and confidence limits based on the determined distribution. It allows saving analyses as separate files. Embedded comments provide information about the statistics.
2. IHStat is a free statistical package developed by the American Industrial Hygiene Association for evaluating occupational samples The program is a preprogramed Excel worksheet that: computes descriptive statistics determines if the distributions are normal or log normally distributed calculates associated confidence limits Ideal for determining compliance with little work What is ihstat?
3. Normal distribution When data resembles a bell shape (i.e. equally clustered around the mean/average) Often occurs with noise data and/or physiological monitoring (ex. blood pressure, heart rate) Log Normal distribution When original data is skewed and does not resemble a bell curve Occurs frequently with air monitored sampling (e.g. particulates) Transforming the data (i.e. taking the natural logarithm of each sample) provides us with a normally distributed variable Lognormal vs normal distributions
4. The remainder of this PowerPoint will walk you through how to use IHStatwith the use of screen shots. Before we can proceed you need to: Download and open IHStat from Moodle or from the AIHA website Ensure macros are enabled in Excel NOTE: if you are unable to enable macros there is a macro free version available on the AIHA website; however, the layout and design is slightly different. How do I use Ihstat?
5. Opening page of ihstat program STEP 2: Click button to enter program STEP 1: Select language preference
6. How to enter exposure limit for comparisons STEP 3: Enter /change occupational exposure limit of hazard you are evaluating by typing in the new value. For example: chlorine has a TLV of 0.5 ppm.
7. How to clear data STEP 4: When you open IHSTAT there may be existing data in the sheet. Clear existing data to input new data by clicking on the eraser (circled).
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10. No/red thumbs down = does not fit distributionIn this example we can see that the data fits a log normal distribution.
11. α level NOTE: α = 0.05 is referring to the confidence level α = 0.05 means we have a confidence level of 95% IHStat uses 95% confidence level for all tests
