Answer:
"Decreasing the sample size."
Explanation:
The margin of error is :
![ME=z* (\sigma )/(√(n))](https://img.qammunity.org/2020/formulas/mathematics/college/olkenpwaju4mmwh7ahyi5fx6918h11w2u5.png)
Therefore, as n decreases, margin of error increases.
In the question we are asked " Which action will not reduce the margin of error."
Therefore, the correct option for which action will not reduce the margin of error is "Decreasing the sample size."