Histogram


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Exercise to produce a histogram of WAZ scores in Kenya East:

       1.  Open keast4j.sav

       2.   In the Data Editor menu, click on Graphs, Histogram

       3.   Select waz from the list of variables and place it in the Variable box using the arrow key

       4.  Click on the box marked Display normal curve and click OK

 

wpe2.jpg (20738 bytes)

 

INTERPRETATION:  This histogram does approximate a normal or Gaussian distribution, as expected for a z-score.  A normal distribution is expected because nutrition status is measured on a continuous scales, where the majority (95%) of any population will lie within 2 SD of the mean, while approximately 2.5% will be significantly above and 2.5% will be significantly below the mean. When referring to nutrition status, the cut-off for z-score is usually within 5 SD of the mean (in either direction) because any measurement beyond that would indicate that an error was made in the data collection (a value this extreme is so unlikely that it is not reliable).  This histogram has been cleaned (all values above and below 5SD have been eliminated) and shows a shift in the mean down the scale to -1.29 SD.  This would indicate that the average child under 5 years (for which the measurements were taken) is at least mildly underweight in comparison with a normal population (and likely the population has a malnutrition problem).

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