As the sample size n is less than 30 normal distribution is used.
The values of x are converted into z by using the formula z= x-u/ s and then the z values are found out from the table.
The limits are found by using the formula x±σz or x±sz where s= σ
As the sample size is 10 which is less than 30 the normal distribution is used.
The probability of x< 2.59 is 0.3446
The probability 2.60<X <2.63 is 0.9484
So lower and upper limits are 2.607 and 2.612
Part A
As the sample size is 10 which is less than 30 the normal distribution is used.
Part B
For given value of x= 2.59 z is obtained =0.4
x= 2.59
z= x-u/ s
z= 2.59-2.61/0.05
z= -0.02/0.05
z=- 0.4
P (X<2.59) = P(-0.4 <Z<0) = 0.5 -0.1554= 0.3446
The probability of x< 2.59 is 0.3446
Part C
For two given values of x= 2.60 and 2.63 z is obtained as =0.2 and 0.4
x1= 2.60
z1= x-u/ s
z= 2.60-2.61/0.05
z= -0.01/0.05
z=- 0.2
x2= 2.63
z2= x-u/ s
z= 2.63-2.61/0.05
z= 0.02/0.05
z= 0.4
P (2.60<X<2.63) = P(-0.2 <Z<0.4)
= P(-0.2 <Z<0)+ P(0 <Z<0.4)
=0.793 + 0.1554= 0.9484
The probability 2.60<X <2.63 is 0.9484
Part D"
p= 0.57
From the table z= 0.045
z= x-u/ s
zs= x-u
zs+u = x
x1= 0.045*0.05 +2.61= 2.61225
x2= 2.61- 0.00225= 2.60775
So lower and upper limits are 2.607 and 2.612
For further understanding of probability calculation click
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