BBS1003 Week 2 complete Question and Answer 2024 final exam

BBS1003 Week 2 complete Question and Answer 2024 final exam How is the odds risk compared to the relative risk? In rare cases, OR is approximately equal to RR, otherwise, ORRR When is relative risk used? It is used when the study involves comparing chance of an event occurring between two groups Formula for the risk Risk = number in a category/total number in group How can the percent increase (decrease) in risk be calculated when comparing 2 groups? Percent increase in risk= Difference in risk / baseline risk * 100% How can the percent increase be calculated when the relative risk has already been determined? Percent increase in risk = (relative risk - 1) * 100% When do we talk about the percent decrease? When the risk is smaller than the baseline, the percent increase will be negative. Define odds The odds compare the chance that an event happens to the chance that it does not. Odds = probability that it happens/probability that it does not happen. Define odds ratio An odds ratio (OR) is a measure of association between an exposure and an outcome. The OR represents the odds that an outcome will occur given a particular exposure, compared to the odds of the outcome occurring in the absence of that exposure. = odds in category 1/odds in category 2 How to calculate expected number? We have to sum up the value in the same row and multiply it with the values of the columns then divide it by the total number of participants. Expected value = (total number of the row)* (total values of the columns)/total number of participants What is the expected value (EV)? It is an anticipated value for an investment at some point in the future. It is calculated by multiplying each of the possible outcomes by the likelihood each outcome will occur and then summing all those values What can we do when we know the EV? By calculating the EV, investors can choose the scenario most likely to give the desired outcome What does the chi-squared X² measure? It measures the difference between the observed and the expected counts between two categorical variables. How to calculate chi- squared X²? For each cell you have to compute: (Observed count - expected count) ²/ expected count. Then the sum these quantities over all cells of the table: X² = sum of (observed count - expected count) ²/ expected count What is a parameter? A number that is a summary characteristics of a population, a random situation or a comparison of populations (it is fixed and unchanged). What is a population parameter? It is used to make it clear that a parameter is associated with a population instead of a sample. Statistical inference The process of using data obtained from a sample to make estimates or test hypotheses about the characteristics of a population. What are the 2 statistical inferences? - Confidence interval: an interval the researcher is sure about - Hypothesis testing: uses sample data to reject a hypothesis about the population What questions to ask about a parameter? 1. Curiosity about something 2. Question about a parameter 3. Collect data appropriate for a parameter 4. Make inferences about the value of the parameter What are parameters and statistics associated with? Parameters with populations and statistics with samples What are the names of the 5 parameters? For categorical variables: 1. One population proportion (or probability) 2. Difference in 2 population proportions For quantitative variables: 3. One population mean 4. Population mean of paired differences (dependent) 5. Difference in 2 population means (independent) Where should the dependent and independent variable be in a cross table? The independent variable should be in the rows while the dependent variable should be in the column What is the relative risk? The ratio of the incidence of the disease among exposed people to the incidence of the disease among unexposed people. Formula: RR= risk in category 1/risk in category 2. When is the relative risk equal to 1? When the risks are the same When is the relative risk bigger or smaller than 1? It is bigger than 1 when the the numerator is bigger and smaller than 1 when the numerator is smaller What is often the denominator in the relative risk? It is the baseline risk: when no additional behavior or treatment is added. In which case can the relative risk not be used? It cannot be used in case-control studies. When is relative risk used? When the study involves comparing chance of an event occurring between 2 groups. Cohort studies Standard deviation of the sample means s.d. (x-bar) = sigma/square root of n (standard deviation multiplied by the m