MOE + confidence intervals

making a claim

1. calculate MOE

2. average MOEs

3. MOE for difference between samples

4. confidence interval

5. make a claim

how to calculate MOE

1 / square root of n

how to find average MOE

(MOE₁ + MOE₂) / 2

how to find MOE for the difference between the samples

1.5 * average MOE

dependent samples: 2 * MOE for one poll

independent samples with the same sample sizes and MOE: 1.414 * MOE

how to calculate confidence interval

(P₁—P₂) ± MOE

= (P₁ + MOE)—(P₂ - MOE)

dependent samples (or paired samples)

the data points in one group are matched or related to those in another group — usually when the same subjects are measured under two conditions

how to calculate MOE when comparing two samples

1. calculate the MOE of difference between the samples

2. calculate the difference between the samples’ results

3. construct the confidence interval (sample_diff ± MOE_diff)

how to calculate the difference between two MOEs

MOE₁ - MOE₂

variance of difference between two independent samples

Var(P₁—P₂) = Var(P₁) + Var(P₂)

a claim can be made when

the confidence interval does not include 0

a claim cannot be made when

the confidence interval does include 0