Biostatistics — Flashcards

Flashcard 51: List the formulas for Standard Error (SE) for the following: 1. Mean 2. Proportion 3. Difference of means 4. Difference of proportions

Answer: 1. **Mean**: \(SE_{mean} = \frac{SD}{\sqrt{n}}\) (Note: use \(n-1\) for small samples < 30, as in t-test) 2. **Proportion**: \(SE_{proportion} = \sqrt{\frac{pq}{n}}\) 3. **Difference of means**: \(SE_{diff\ mean} = \sqrt{\frac{SD_1^2}{n_1} + \frac{SD_2^2}{n_2}}\) - Or: \(s \sqrt{\frac{1}{n_1} + \frac{1}{n_2}}\) where pooled \(s = \sqrt{\frac{\sum(X_1 - \bar{X}_1)^2 + \sum(X_2 - \bar{X}_2)^2}{n_1 + n_2 - 2}}\) 4. **Difference of proportions**: \(SE_{diff\ prop} = \sqrt{\frac{p_1q_1}{n_1} + \frac{p_2q_2}{n_2}}\)

Flashcard 52: Regression is _____ type in qualitative variation

Answer: logistic

Flashcard 53: _____ is the probability that when the disease is absent, the test is negative

Answer: Specificity

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Flashcard 54: Kaplan-Meier analysis method is for _____

Answer: survival statistics

Flashcard 55: formula for sample size calculation

Answer: n = 4pq / L²

Extra: n = Sample size p = Prevalence q = 100 – p L = Allowable error (Permissible error) This formula is derived from n = Z²pq/d², where Z ≈ 2 for a 95% confidence interval (Z² ≈ 4).

Flashcard 56: test of significance for outliers is _____ test

Answer: Dixon's Q

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Flashcard 57: _____ plots are used to plot correlation

Answer: scatter

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Flashcard 58: de4dcbb8321648c59eb0eb9463b92568-ao-2

Answer: population growth rate

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Flashcard 59: _____ is used to compare a new test with a gold standard to assess agreement.

Answer: Bland-Altman analysis

Flashcard 60: Formula for Standard Deviation for Grouped data, when, \(X_g = Mid-point \ of \ each \ group\) and, any convenient group may be taken as working mean (\(w\)) → \(f = frequency \ of \ each \ group\) → Working units are denoted as, _____ where, \(i = Group \ interval\) → Then, deviation of group in working units is derived by \(f \times x\) → Squared deviation of groups is \(= f \times x^2\) Mean in working units is given by : \(\bar x = \frac {\sum fx}{n}, \) and True Mean is given by \(\bar X = w \ + \ \bar x \times i\) Standard deviation in working units is _____\)}} True SD is, _____

Answer: \(x = \frac {X_g - w}{i}\)