# Sample size calculation on IYCF indicators in small scale survey

This question was posted the Infant and young child feeding interventions forum area and has 11 replies.

### Anonymous 512

Nutrition Specialist

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22 Dec 2010, 14:05

### Mark Myatt

Epidemiologist at Brixton Health

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23 Dec 2010, 11:18

### Tamsin Walters

en-net moderator

Forum moderator

23 Dec 2010, 12:04

*From Kirk Dearden:*A couple of thoughts and questions: 1. I'm assuming you are conducting a survey that is principally designed to capture something other than IYCF and that the nutrition questions are simply being added to that questionnaire (which appears to be focused first and foremost on mortality). Knowing this helps one decide on the most appropriate sampling strategy. 2. It seems to me that there should be 37 infants 0-5.9 months of age, not 33 because 333 divided by 9 age intervals between 6 and 59.9 months = 37 per 6-month age interval. 3. I don't follow how there will be 367 respondents in 408 households. Also, if the sample size goes up from 408 to 514, I wouldn't consider this a massive increase. Perhaps I am missing something. 4. I don't know all of the logistics and costs associated with conducting the survey in this particular context; however, given that a lot of the expense associated with a survey is finding the households in the first place and that the IYCF questions take up about 2 pages of a questionnaire (i.e., it wouldn't take long to administer them), I'd recommend conducting the IYCF survey in each one of the 514 houses where there is a child 0-59.9 months of age. If that simply isn't feasible, then you can simply collect IYCF data from the 408 households. In other words, they'd collect data from 79.4% of the households involved in the mortality survey (408/514). Perhaps the easiest way to do this is to ask during the mortality survey for age-eligible children (0-59.9 months) in each household in each cluster. Once you reach the necessary 25 kids for a given cluster (370 sample size divided by 15 clusters), they stop collecting IYCF data on kids for that particular cluster. Hopefully, this is of some help. Kirk

### Kirk

Associate Professor, Boston University

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23 Dec 2010, 13:31

### Marie McGrath

ENN

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23 Dec 2010, 15:18

### Mark Myatt

Epidemiologist at Brixton Health

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30 Dec 2010, 16:03

### Tamsin Walters

en-net moderator

Forum moderator

31 Dec 2010, 10:43

*From Bradley Woodruff*: Dear All: Thanks to Mark for his very clear explanation. One additional point you should remember is that the standard IYCF indicators, as recommended by WHO and UNICEF, apply to age groups of differing width, and some of these age groups are quite narrow. For example, introduction of complementary foods is calculated only in children 6-8 months of age, while ever breastfed is calculated for all children less than 24 months of age. Therefore, if you are recruiting children in different age groups from the same sample and you are calculating a sample size for more than one IYCF indicator, you must find a common unit into which the sample size for each indicator can be converted so that you can compare the various sample sizes you have calculated. For example, if you calculate that the sample sizes for introduction of complementary foods and ever breastfed are both 333, as recommended by Mark, and you are conducting a household survey, which indicator requires visiting more households? You do not know this until you convert the sample size of 333 children 6-8 months of age and the sample size of 333 children 0-23 months of age into the number of households you must visit to find the 333 children in each age group. Let's work through an example. If we know, for example, that 18% of the population is less than 5 years of old and that the average household size is 5.5 persons, we can calculate the average number of children in each age group who will be found in each household. If we assume that infant mortality and child mortality are neglible (which may not be true in some populations), then about 40% of the under five population is under two, and 7.2% of the population is less than 24 months of age (18% x 0.4). The age group 6-8 months represents 3 months of the 59 months in the first 5 years of life; therefore, children 6-8 months make up 0.92% of the population (18% x [3/59]). Now multiply the average household size by the proportion of the total population made up of each target group to get the average number of children in each age group per household. For children less than 24 months, this would be 0.4 child per household (0.072 x 5.5 = 0.396). For children 6-8 months of age, this would be 0.05 children per household (0.0092 x 5.5 = 0.05). Now to calculate how many households you will have to visit to find the 333 children for each indicator. For children less than 24 months of age, you will have to go to about 2.5 households to find one eligible child (1 / 0.4). To find 333 children, you will need to visit 833 households (333 / 0.4). For children 6-8 months of age, you will have to go to 20 households to find one eligible child (1 / 0.05). To find 333 children, you will need to visit 6,660 households! (333 / 0.05) Therefore, you will have to go to many more households to find children for the indicator introduction of complementary food than for the indicator ever breastfed. So even though the sample size for children may be the same, when it comes to the sampling unit (in this example, households) the sample sizes are very different. In fact, because some of the IYCF indicators, such as introduction of complementary foods, are calculated in children from such a narrow age range, it is essentially impractical to measure them in household surveys. You may need to find some other sampling frame, such as population registrations or MCH registrations, from which to sample such children. Regards, Woody

### Mark Myatt

Epidemiologist at Brixton Health

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3 Jan 2011, 10:05

### Alexandra Rutishauser-Perera

International Medical Corps

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1 Oct 2012, 20:56

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