SAMPLING AND ESTIMATION THEORIES 589
J
10 samples of the materials. The mean and
standard deviation of the results are found
to be 5.17 MPa and 0.06 MPa respectively.
Determine the 95% confidence interval for
the mean of the ultimate tensile strength of
the material.
[5.133 MPa to 5.207 MPa]
- Use the data given in Problem 1 above to
determine the 97.5% confidence interval for
the mean of the ultimate tensile strength of
the material.
[5.125 MPa to 5.215 MPa]
- The specific resistance of a reel of German
silver wire of nominal diameter 0.5 mm is
estimated by determining the resistance of
7 samples of the wire. These were found to
have resistance values (in ohms per metre) of:
1.12, 1.15, 1.10, 1.14, 1.15, 1.10 and 1.11
Determine the 99% confidence interval for
the true specific resistance of the reel of wire.
[1. 10 m−^1 to 1. 15 m−^1 ]
- In determining the melting point of a metal,
five determinations of the melting point are
made. The mean and standard deviation of the
five results are 132.27◦C and 0.742◦C. Calcu-
late the confidence with which the prediction
‘the melting point of the metal is between
131.48◦C and 133.06◦C’ can be made.
[95%]
