Question 1178604
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Hi
Normal distribution:  μ = 30min and  σ =6   
n = 10  mean = 20min 
Ho:  μ = 30
Ha:  μ < 30
a=0.10, one-tailed:df9  t = 1.38 critical value

 t-value = -10(√10) /6 = -5.27
|-5.27| > 1.38
Reject Ho, evidence indicates mean is < 30min
Wish You the Best in your Studies.
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