Deliverable: Working Tableau workbook around data types and desirable contents
Freelancer sought: Expert Tableau builder with understanding of statistics (will need some statistics calculations in report)
1) to create a type of "psychometric" view in Tableau. Sample data can be provided. Basically, each individual in the data needs to A) have a total score calculated, B) be categorized into a "performance group" like upper 20% or lower 20% based upon their score compared to all other individuals. Then each group's performance on various questions is displayed visually as in the image below. Each line would represent an answer choice. This is basically what is called a "distractor analysis" like here (see also Figure 1): [login to view URL] . Ideally this would be displayed with filters as shown in Figure 2, with the ability to compare two different data points.
2) I have need to convert specific answers into a "generic" type that can be exported if needed. For example, if the correct one is "quadratic formula", I need this recoded as "A" or "1" (A or 1 would always be the right answer. If there are two remaining incorrect ones (distractors), then I need it to assign a "B/2" and "C/3" to those choices. I have tried to do this, but I need someone to check this logic and see if there is an easier way to code this inside Tableau.
3) I have need to find three calculations inside Tableau that can be filtered as needed based on individual characteristics (e.g., region, exam language, etc). The first is the "difficulty", which is simply the % of people that get it correct. The last two of these values give an idea of the psychometric idea of "discrimination." The first is a point-biserial correlation, which is just like a correlation coefficient between a score (which would be a SUM of the correct indicators for each individual) and a specific item outcome (1/0 where 1 = right and 0 = wrong). This formula is shown in Figure 3. The last formula is just a subtraction of percentile ranks ... 73rd percentile minus 27th percentile (see Figure 4). Each of these numbers are statistics on the individual ITEMS.
4) Finally, I need to create overall summaries for the entire collection of items. This would include the average difficulty (% correct), an average for each of the 2 discriminations listed in #3, and something called a KR-20 metric. This KR-20 calculation in Excel is shown here: [login to view URL] . I need this to be in a type of "report card" as shown in Figure 5. All of these are aggregates of the total.
23 freelancers are bidding on average $36/hour for this job
Hi there, As an Power BI expert with extensive knowledge in statistics i can help you with this project. Please feel free to contact me to discuss further details. Best regards, Miljan