Data and analysis

 What kind of data are available in orthopaedics ?
   1.Non-continuous, qualitative or categorical. Gu 1, 2, 3 -Analysed using Chi-squared or Fischer's exact test 

    2.Continuous or variable data e.g. height, age, knee valgus angle

    These data are often not always -Gaussian distribution e.g. symmetrical bell-shaped curve.

    Continuous data described using Mean, Median and Mode.

    With Normal distribution, mean/median and mode are equal.

What is dispersion ?

    It is a variability of a data set.If all values are zero, dispersion is zero.

    Measured using Quartiles, SD and Variance.

    Variance- how much it deviates from mean.

    SD- square root of variance (to give same original dimension as data )

    Standard error of mean (SEM) - measures how closely sample mean of data set approximates to                 population mean.

        SEM = SD / √n


     In a normal distribution data - comparison done using parametric tests such as student T-test.

    Non normal distribution, student's T-test is used.

    Sensitivity

                ability of a test to detect cases that are positive.

                all test with positive results/all cases truly positive * 100

     Sensitivity

                ability of a test to detect cases that are negative

                all negative tests results/cases that are negative *100

            

What factors are need to be looked for in outcome scoring system ?
                accuracy = how accurate it is compared with the gold standard.

                validity   = extent to which an experiment value represents a true value

                reliability = ability to repeat the test

                ease of use = assessment method should be appropriate and not too long ,complex or cumbersome. 

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