Two sample inference.

Hi guys,

Please help me with this problem.

Two types of plastic is suitable for the use by an electronic component manufacturer, The braking strengthof the plastic is important.
It is known tht sigma1=sigma2=7 kN/m^2.
From a random sampleof size n1=10. N2=12. Xbar1=1120 Xbar2= 1070.

The company will not adopt plastic 1 unless its mean breaking strenth exceeds that of plastic 2 by at least 10 kN/M^2

Q1:Based on the sample indormation, should it use plastic 1, alphy=0.05.

Q2:Find the P value?

Please help :)

Thank you.


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Ok cool :) i can understand,

Parameters: mean1, mean2,

Hull hypothesis :mean1-mean2 <= 10
Alt hypothesis mean1 -mean2 > 10 .

Test statistic: variance known, independent, would say Z test,
if Z0xbar1-xbar2-delta/sqrt(var1/n1 +var2/n2)

Reject null hypothesis


I get a Z0 value 13.345.

I am comfused with the units,

If xbar1 =112 instead of 1120 and xbar2=107 instead of 1070 then the z value = -1.668,
Which can be compared to z alpha,

If strength is in Mpa then xbar1=1120 x10^6 Pa =1120 x10^3 kN/m^2.


I cant find the correct units?
Is my test statistic correct?
Is the units in kPa (nothing is stated)

The z value does not come in the table and should then be equal to one?

Any advice would help :)