HLT 362V Topic 2 Discussion 2
Using the research article selected for DQ 1, identify three key questions you will ask and answer when reading the research
... [Show More] study and why these questions are important. When responding to peers, provide other questions and answers that could be considered in relation to the peers’ studies.
1. What is Spearman’s rank correlation coefficients?
The Spearman’s Rank Correlation Coefficient is the non-parametric statistical measure used to study the strength of association between the two ranked variables. This method is applied to the ordinal set of numbers, which can be arranged in order, i.e. one after the other so that ranks can be given to each.
In the rank correlation coefficient method, the ranks are given to each individual on the basis of its quality or quantity, such as ranking starts from position 1st and goes till Nth position for the one ranked last in the group (Business Jargons, n.d.).
The formula to calculate the rank correlation coefficient is:
Where, R = Rank coefficient of correlation
D = Difference of ranks
N = Number of Observations
2. What is a Z test?
A Z-test is a type of hypothesis test. Hypothesis testing is just a way for you to figure out if results from a test are valid or repeatable. For example, if someone said they had found a new drug that cures cancer, you would want to be sure it was probably true. A hypothesis test will tell you if it’s probably true, or probably not true. A Z test, is used when your data is approximately normally distributed (Statistics how to, 2014).
You would use a Z test if:
• Your sample size is greater than 30.
• Data points should be independent from each other. In other words, one data point isn’t related or doesn’t affect another data point.
• Your data should be normally distributed. However, for large sample sizes (over 30) this doesn’t always matter.
• Your data should be randomly selected from a population, where each item has an equal chance of being selected.
• Sample sizes should be equal if at all possible.
How do I run a Z Test?
Running a Z test on your data requires five steps:
1. State the null hypothesis and alternate hypothesis.
2. Choose an alpha level.
3. Find the critical value of z in a z-table.
4. Calculate the z test statistic (see below).
5. Compare the test statistic to the critical z value and decide if you should support or reject the null hypothesis.
You could perform all these steps by hand (Statistics how to, 2014).
3. What does a cross-sectional study mean?
Cross-sectional study design is a type of observational study design. In a cross-sectional study, the investigator measures the outcome and the exposures in the study participants at the same time. Unlike in case–control studies (participants selected based on the outcome status) or cohort studies (participants selected based on the exposure status), the participants in a cross-sectional study are just selected based on the inclusion and exclusion criteria set for the study. Once the participants have been selected for the study, the investigator follows the study to assess the exposure and the outcomes. Cross-sectional designs are used for population-based surveys and to assess the prevalence of diseases in clinic-based samples. These studies can usually be conducted relatively faster and are inexpensive. They may be conducted either before planning a cohort study or a baseline in a cohort study. These types of designs will give us information about the prevalence of outcomes or exposures; this information will be useful for designing the cohort study. However, since this is a 1-time measurement of exposure and outcome, it is difficult to derive causal relationships from cross-sectional analysis. The prevalence of disease in cross-sectional studies can be estimated. One is also able to estimate the odds ratios to study the association between exposure and the outcomes in this design (Setia, 2016).
These three questions are important as the first question relates to the ranking order of the patients perception of risk for coronary artery disease, the second question shows how to determine if the hypothesis is valid, and the third question relates the method of the study and inclusion/exclusion factors.
References:
Business Jargons (n.d). Spearman’s rank correlation coefficient. Retrieved from: https://businessjargons.com/spearmans-rank-correlation-coefficient.html
Setia M. S. (2016). Methodology Series Module 3: Cross-sectional Studies. Indian journal of dermatology, 61(3), 261-4.
Statistics how to (2014). Z Test: Definition and two proportion z test. Retrieved from: https://www.statisticshowto.datasciencecentral.com/z-test/ [Show Less]