Household Income and Expenditure Survey 2019

SAMPLE SIZE:
In determining an appropriate sample size for a survey of this nature, numerous factors come into the equation. These include:

a) The degree of accuracy required for key estimates;
b) The population size of the country;
c) The manner in which the sample is selected;
d) Cost or staffing constraints which may exist;
e) Whether or not estimates are required for sub-populations;
f) The level of variability in the data being collected.

Each of these factors have different magnitudes of importance, but the major priority should always be on selecting a sample big enough to produce results of suitable accuracy. Many of these issues are generally known as well - for instance:

· A user group may pre-specify what level of accuracy they may wish to achieve for the survey
· The population of a country can normally be estimated to a reasonable level of accuracy
· The sample selection technique adopted is known
· Cost and staff constraints are generally known, and
· A user group can once again provide information on whether estimates for sub-populations are required.

The Marshall Islands 2020 Household Income and Expenditure Survey (HIES) aims to release outputs at the Urban Rural level and National level.

The sampling strategy has been developed around a stratification of urban and rural domains of the Marshall Islands. This stratification aims to improve the robustness of the indicators at urban and rural level. The urban sector has been stratified in 2 different atolls (Majuro and Kwajalein) and the rural region has been stratified in group of atolls that show similarities as follow:

• Rural 1: peri urban atolls; located close to Majuro and Kwajalein (Arno, Mili)
• Rural 2: most important rural atolls with facilities (boarding schools; health center…) (Jaluit; Wotje)
• Rural 3: atolls where population benefit from US Government for nuclear testing (Enewatak, Kili, Utirik)
• Rural 4: other atolls

The targeted sample size has been determined around 880 households based on the results of the previous 2011 population census that provided the mean and standard deviation of the total cash household income at the strata level:

The cluster size has been determined at 12 households.

-Urban 1 & 2: respectively 400 and 150 households spread across 33 and 13 EAs lead to 7.9% RSE in Urban domain
-Rural: respectively 2, 3, 10 and 13 EAs in rural1, 2, 3 and 4 (24, 36, 120 and 150 households) lead to 7.3% RSE in Rural domain
-At the National level this total sample size of 880 households spead across those 6 stratas as mentioned lead to a RSE of 7.1%

SAMPLE SELECTION:
The 2020 Marshall Islands HIES is based on a stratified cluster sampling strategy. The households are selected in 2 steps:

• Step1: the random selection of EA based on the sampling strategy parameters (Primary sampling unit)
• Step2: the random selection of 12 households (+6 replacements) within each selected EA

The final probability of selection combines both probabilities of EA getting selected within the strata and households getting selected with the EA.