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Group 4 element - Wikipedia, the free encyclopedia (202 words) |
 | A Group 4 element is one in the series of elements in group 4 (IUPAC style) in the periodic table, which consists of titanium (Ti), zirconium (Zr), hafnium (Hf) and rutherfordium (Rf). |
| All of these elements are classed in Group 4 because their valence shell holds four electrons. |
| Rutherfordium can only be produced in the laboratory and has not been found in nature. |
| Group 4: Homework 8 (3205 words) |
| The sample size(per group) ranges from 2263 at a 5% prevalence of disease in exposed controls to 521 at a 50% prevalence of disease in exposed controls when the OR is 1.5. |
| When OR is 3.0, the sample size(per group) ranges from 239 at a 5% prevalence of disease in exposed controls to 79 at a 50% prevalence of disease in exposed controls. |
| Group #4 Sample Size Prevalence of exposure Power OR cases control.05.90 1.5 2262.81 2262.81.20.90 1.5 717.35 717.35.50.90 1.5 520.27 520.27.05.90 3.0 238.15 238.15.20.90 3.0 86.71 86.71.50.90 3.0 78.83 78.83 For constant alpha and beta error levels, as OR and prevalence of exposure increase, a smaller sample size is needed to detect differences. |
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