Answer: the minimum sample size needed = 145
Step-by-step explanation:
Formula for sample size:
[tex]Sample \ size =(\dfrac{z^*\times standard\ deviation}{margin \ of \ error})^2[/tex]
, where z* = Critical z-value
Given: Standard deviation = 2.15
Margin of error = 0.35
Z* for 95% confidence = 1.96
Sample size = [tex](\frac{1.96\times2.15}{0.35})^2[/tex]
[tex]=(12.04)^2\\\\=144.9616\approx145[/tex]
Hence, the minimum sample size needed = 145