Survey data quality Survey data quality Objectives assessing

Survey data quality

Survey data quality Objectives • assessing age and sex structure. – Sex Ratio – Age Distribution 2

Survey data quality Sex ratio • proportion of males to females • sex ratio for 0 to 4 -year-old normally between 101 and 108 boys per 100 girls. • Use census or international databases – https: //esa. un. org/unpd/wpp/Dataquery/ • Can indicate selection bias during survey 3

Survey data quality Sex ratio • For all sampled children • We can also do a Chi-squared and look at the pvalue 4

Survey data quality Sex ratio : example • • Sex Ratio Test Expected proportion male = 0. 5145 Observed proportion male = 0. 5017 X-squared = 0. 5225, p = 0. 4698 5

5 min 6 Snapshot Question In what cases can the sex ratio differ from 1: 1?

Survey data quality Age ratio • For all sampled children • We can calculate an expected value using census data • We can also do a X-squared and look at the pvalue 7

Survey data quality Age ratio : example • Age Ratio Test • Expected age ratio = 0. 8500 • Expected proportion aged 6 - 29 months = 0. 4595 • Observed age ratio = 0. 8654 • Observed proportion aged 6 - 29 months = 0. 4639 • X-squared = 0. 0531, p = 0. 8178 8

Survey data quality Age Distribution • year-centred age groups • Population pyramids • Use census or international databases – https: //esa. un. org/unpd/wpp/Dataquery/ • Can indicate selection bias during survey 9

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Survey data quality Age distribution : example • Pearson's Chi-squared test • data: table(svy$ycag, svy$sex) • X-squared = 1. 2675, df = 4, p-value = 0. 8669 13

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Survey data quality Conclussions • Sex Ratio and Age Ratio can be quickly calculated to see if the survey is similar to the population • If the survey data is not representative of the population it tells us nothing about the population • You can confirm statistical significance with Chi -sq tests but be careful when sample sizes are very big January 2019 Addis Ababa 15

Excercise 3 • To be done in couples • The file ex 03. csv is a comma-separated-value (CSV) file containing anthropometric data from a SMART survey in Kabul, Afghanistan. • It is reported that there about 2. 658 million boys and 2. 508 million girls aged between zero and four years in Afghanistan (2012 estimates) • You can do Chi-square easily here: https: //www. medcalc. org/calc/comparison_of_pro portions. php 16

Excercise 3 • Calculate the sex ratio • Build a population pyramid and discuss • Calculate age ratio (if time) 17

How to use the online calculator 18