Behavioral Science - Epidemiology / Biostatistics Flashcards

Question

Accuracy

Answer 1

* The trueness of test measurements (validity). * The absence of systematic error or bias in a test. * Systematic error—reduces accuracy in a test.

Answer 2

* Definition * Nonrandom assignment to participate in a study group. * Most commonly a sampling bias. * Examples * Berkson bias * A study looking only at inpatients * Loss to follow-up * Studying a disease with early mortality * Healthy worker and volunteer biases * Study populations are healthier than the general population * Strategies to reduce bias * Randomization * Ensure the choice of the right comparison/reference group

Answer 3

* Definition * Awareness of disorder alters recall by subjects * Common in retrospective studies. * Example * Patients with disease recall exposure after learning of similar cases * Strategy to reduce bias * Decrease time from exposure to follow-up

Answer 4

* Definition * Information is gathered in a way that distorts it. * Example * Hawthorne effect — groups who know they’re being studied behave differently than they would otherwise * Strategy to reduce bias * Use of placebo control groups with blinding to reduce influence of participants and researchers on experimental procedures and interpretation of outcomes

Answer 5

* Definition * Subjects in different groups are not treated the same. * Example * Patients in treatment group spend more time in highly specialized hospital units * Strategy to reduce bias * Use of placebo control groups with blinding to reduce influence of participants and researchers on experimental procedures and interpretation of outcomes

Answer 6

* Definition * Researcher’s belief in the efficacy of a treatment changes the outcome of that treatment * aka Pygmalion effect; self-fulfilling prophecy * Example * If observer expects treatment group to show signs of recovery, then he is more likely to document positive outcomes * Strategy to reduce bias * Use of placebo control groups with blinding to reduce influence of participants and researchers on experimental procedures and interpretation of outcomes

Answer 7

* Definition * When a factor is related to both the exposure and outcome, but not on the causal pathway * Factor distorts or confuses effect of exposure on outcome * Example * Pulmonary disease is more common in coal workers than the general population * However, people who work in coal mines also smoke more frequently than the general population * Strategies to reduce bias * Multiple/repeated studies * Crossover studies (subjects act as their own controls) * Matching (patients with similar characteristics in both treatment and control groups)

Answer 8

* Definition * Early detection is confused with increased survival * Seen with improved screening techniques. * Example * Early detection makes it seem as though survival has increased, but the natural history of the disease has not changed * Strategy to reduce bias * Measure “back-end” survival (adjust survival according to the severity of disease at the time of diagnosis)

Answer 9

* Mean = (sum of values)/(total number of values). * Median = middle value of a list of data sorted from least to greatest. * If there is an even number of values, the median will be the average of the middle two values. * Mode = most common value.

Answer 10

* Standard deviation = how much variability exists from the mean in a set of values. * Standard error of the mean = an estimation of how much variability exists between the sample mean and the true population mean. * σ = SD, n = sample size * SEM = σ / sqrt(n) * SEM decreases as n increases

Answer 11

* Gaussian, also called bell-shaped. * Mean = median = mode.

Answer 12

* Suggests two different populations * e.g., metabolic polymorphism such as fast vs. slow acetylators; suicide rate by age

Answer 13

* Typically, mean \> median \> mode. * Asymmetry with longer tail on right.

Answer 14

* Typically, mean \< median \< mode. * Asymmetry with longer tail on left.

Answer 15

* Hypothesis of no difference * e.g., there is no association between the disease and the risk factor in the population

Answer 16

* Hypothesis of some difference * e.g., there is some association between the disease and the risk factor in the population

Answer 17

* Stating that there is an effect or difference when one exists * Null hypothesis rejected in favor of alternative hypothesis * Stating that there is not an effect or difference when none exists * Null hypothesis not rejected

Answer 18

* Definition * Also known as false-positive error * Stating that there is an effect or difference when none exists * Null hypothesis incorrectly rejected in favor of alternative hypothesis * **_α_ = you s**_a_**w a difference that did not exist (e.g., convicting an innocent man).** * α & p * α is the probability of making a type I error. * p is judged against a preset a level of significance (usually \< .05). * If p \< 0.05, then there is less than a 5% chance that the data will show something that is not really there.

Answer 19

* Definition * Also known as false-negative error. * Stating that there is not an effect or difference when one exists * Null hypothesis is not rejected when it is in fact false * **_β_ = you were **_b_**lind to a difference that did exist (e.g., setting a guilty man free).** * β & power * β is the probability of making a type II error. * β is related to statistical power (1 – β), which is the probability of rejecting the null hypothesis when it is false. * Increase power and decrease β by: * Increasing sample size * **There is power in numbers.** * Increasing expected effect size * Increasing precision of measurement

Answer 20

* Pools data and integrates results from several similar studies to reach an overall conclusion. * Increase statistical power. * Limited by quality of individual studies or bias in study selection.

Answer 21

* Definition * Range of values in which a specified probability of the means of repeated samples would be expected to fall. * Equation * CI = range from [mean – Z(SEM)] to [mean + Z(SEM)]. * 95% & 99% CI * For the 95% CI, Z = 1.96. * The 95% CI (corresponding to p = .05) is often used. * For the 99% CI, Z = 2.58. * If the 95% CI for a mean difference between 2 variables includes 0 * Then there is no significant difference and H0 is not rejected. * If the 95% CI for odds ratio or relative risk includes 1 * H0 is not rejected. * If the CIs between 2 groups do not overlap * Significant difference exists. * If the CIs between 2 groups overlap * Usually no significant difference exists.

Answer 22

* Checks differences between means of 2 groups. * **Tea is meant for 2** * Example: comparing the mean blood pressure between men and women.

Answer 23

* Checks differences between means of 3 or more groups. * **3 words: ANalysis Of VAriance** * Example: comparing the mean blood pressure between members of 3 different ethnic groups.

Answer 24

* Checks difference between 2 or more percentages or proportions of categorical outcomes (not mean values). * **Pronounce Chi-tegorical** * Example: comparing the percentage of members of 3 different ethnic groups who have essential hypertension.

Answer 25

* Definition * r is always between -1 and +1. * The closer the absolute value of r is to 1, the stronger the linear correlation between the 2 variables. * Positive vs. negative r value * Positive r value --\> positive correlation. * Negative r value --\> negative correlation. * Coefficient of determination = r² (value that is usually reported).

Answer 26

* **_P_**rimary * **_P_**revent disease occurrence (e.g., HPV vaccination). * **_S_**econdary * **_S_**creening early for disease (e.g., Pap smear) * **_T_**ertiary * **_T_**reatment to reduce disability from disease (e.g., chemotherapy) * **Quaternary** * Identifying patients at risk of unneccessary treatment, protecting from the harm of new interventions

Answer 27

* Both * Federal programs that originated from amendments to the Social Security Act. * Medicare * Available to patients ≥ 65 years old, \< 65 with certain disabilities, and those with end-stage renal disease. * **MedicarE is for Elderly** * Medicaid * Joint federal and state health assistance for people with very low income. * **MedicaiD is for Destitute**