At a factory, 50-metre lengths of cotton thread are wound onto bobbins. Due to fraying, it is common for a length, l cm, of cotton to be removed after it has been wound onto a bobbin. The following table summarises the lengths of cotton thread removed from 200 bobbins.

a. Calculate an estimate of the mean length of cotton removed.

b. Use your answer to part a to calculate, in metres, an estimate of the standard deviation of the length of cotton remaining on the 200 bobbins.

Transcribed Image Text:

Length removed 0