Question

Boron has two naturally occurring isotopes, ¹⁰B and ¹¹B. The ratio of the numeric abundances may vary for samples derived from diverse natural sources.

A	4.02668	E	4.02709
B	4.02553	F	4.02747
C	4.02404	G	4.02480
D	4.02417	H	4.02598

Sample E was analyzed five times giving
4.02709 and s = 0.00007.
The 99% confidence interval for sample E is:
4.02709± ???

Answer 1

Level of Significance ,    α =    0.01          
degree of freedom=   DF=n-1=   4          
't value='   tα/2=   4.6041   [Excel formula =t.inv(α/2,df) ]      
                  
Standard Error , SE = s/√n =   0.0001   / √   5   =   0.000031
margin of error , E=t*SE =   4.6041   *   0.00003   =   0.000144
                  
confidence interval is       

4.02709± 0.000144

           

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