fundamentals of Research
The entire research turns around the null hypothesis(H0) and alternative hypothesis (Ha). A research hypothesis is development of the research question (s), including a supportive hypothesis and objectives created by researchers. Alternative Hypothesis (Ha) is the hypothesis that is believed to be true by the researcher; however, it may or may not be accepted.
Null hypothesis(H0) is accepted when NO statistical difference is detected between treated group (p-value > 0.05 (or 5%)). On the other hand, alternative hypothesis (Ha) is accepted (p-value < 0.05) when Null hypothesis(H0) is rejected as Ha is the opposite of H0 (p-value < 0.05 (or 5%)). For example, a drug manufacturer testing a new calcium channel blocker. They are comparing its blood pressure lowering ability against placebo. The null hypothesis (Ho) would be that there is no difference between the two groups. The alternative hypothesis (Ha) would be that there is a difference in blood pressure. If the researchers found that new calcium channel blocker significantly lowers blood pressure more than placebo with a p-value of 0.002. So, we would reject the null hypothesis in this case and accept the alternative hypothesis (Ha).
State the type or direction of the effect. A two-tailed test is when studying the differences in either direction at the same time. In other words, the 2-tailed tests for the possibility of positive or negative differences (e.g., increase and decrease at the same time). In contrast, the one-tailed test is appropriate if you only want to determine if there is a difference between groups in a specific direction (e.g., we test for reduction). Should note that two-tailed test requires larger sample size compared with one-tailed test. For example, if we study drug X for blood sugar level (BSL), and the alternative hypothesis is drug X differences on BSL, then we will use a two-tailed test as there is a possibility of positive or negative differences (e.g., increase and decrease at the same time). On the other hand, if we study drug X for blood sugar level (BSL), and the alternative hypothesis is that drug X reduces BSL, then we will use a one-tailed test as we are studying only one possibility (reduction only).
Remember always, every research study possesses its limitations, regardless of how carefully it was conducted. As possible, you should minimize the limitations. Also, you should be able to understand any study limitation (s) to apply its results to medical practice.
To assess a research question, the researcher should ask, “is it feasible, interesting, novel, ethical, relevant”. These are known as the FINER criteria.
The PICOT format is a useful format to refer to the four components of a good research questions that will facilitate the identification of relevant information.
(P) Population of interest
(I) Intervention being studied.
(C) Comparison group (or to what is the intervention being compared).
(O) Outcome (dependent variable) of interest.
(T) Time for follow-up
Type of Errors
internal and external validity in research
Validity of a study is a general issue of whether or not there are imperfections in the study design, data collection, or methods of data analyses that might distort the conclusions about an exposure-disease relationship. Validity of the study can be classified as internal and external validity.
Categorical versus Continuous Variables
Continuous (Parametric) Variables
Correlation & Causation
Dependent versus Independent Variables
prevalence versus incidence
Rate versus proportion
A proportion can range from 0 to 100, and the numerator is contained in the denominator.
A rate can range from 0 to infinity, and the numerator is the number of cases, whereas the denominator is the person-time at risk.