Solution:
Given in the question
Average = 8
Standard deviation = 2.1
Here also given p-value = 0.15
From z score we found Z score = -1.0364
Z = (Xbar-mean)/SD
-1.0364 = (Xbar-8)/2.1
Xbar =8 - 2.18
Xbar = 5.82
So 15th percentile is 5.82 degree celcius.
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