# Formula

n=[4 (r) (1 - r) (deff) (1.1)] / [(.12r )2(p)(ave-size)]

where

n is the required sample size, expressed as number of households, for the KEY indicator

4 is factor to achieve 95 percent level of confidence,

r is anticipated prevalence (coverage) rate for key indicator,

1.1 is factor to raise sample size by 10 percent for potential nonresponse,

deff is shortened symbol for design effect,

0.12r is margin of error to be tolerated, defined as 12 percent of r (12 percent thus represents the relative sampling error of r),

p is proportion of total population that smallest group comprises, and

ave-size is average household size.

You may use the table on the next page instead of formula if all conditions are satisfied for that table in your country.