chemical supplier wishes to determine whether a new preservative will provide

longer shelf life for bread. A random sample of 10 bakeries was selected and asked to

provide the supplier with a fresh loaf of standard bread each using their regular

preservative. Another random sample of 8 bakeries was selected and asked to use the new

preservative in a batch of dough and then provide the supplier with a fresh loaf of

standard bread using the new preservative. The results of the experiment are as follows:

Shelf life ( days ) 5.7, 4.2, 6.5, 3.4, 6.1, 5.3, 4.9, 3.7, 2.8

(Old Preservative )

Shelf life ( days ) 6.3, 3.9, 6.7, 3.6, 6.3, 5.7, 5.2, 3.7

(New Preservative )

The new preservative would be used if it increases mean shelf life by at least 1/2 day.

Using 10% level of significance, would you suggest using the new preservative?