Question

Using Data below, there is a 99% chance that the true population standard deviation is above ( ).

Please include Excel Calculations.

Strength
279.3	280.7	245.9	269.8	256.9	252.6	257
263.8	265.9	272.5	250.6	255.6	242.5	268.1
274.2	248.2	249.8	265.3	256.1	274	250.3
259.5	283.8	242.2	270.9	265.1	264.7	275.1
257.1	267.4	279.3	243.9	243.3	271.4	261.5
253.4	259.6	259.2	265.4	267.5	267.5	255.5
259.6	252	286.7	256.1	261.9	252.7	267.1

Answer 1

Variance = 124.2293	=VAR(A1:A49)
Standard deviation = 11.14582	=STDEV(A1:A49)

Excel:

124.229337	VAR(A1:A49)	n	49
11.1458215	STDEV(A1:A49)
XL^2	26.51059101	CHISQ.INV(0.005,48)
XU^2	76.96876773	CHISQ.INV.RT(0.005,48)
CI
Lower limit	77.47308862	(n-1)*S^2/XU^2
Upper limit	224.9292806	(n-1)*S^2/XL^2

there is a 99% chance that the true population standard deviation is above 77.4731 and below 224.9293