1.As head of a department of a consumers' research organization, you have the responsibility for testing and comparing lifetimes of four brands of electric bulbs. Suppose you test the lifetime of three electric bulbs of each of the four brands. The data is shown below, each entry representing the lifetime of an electric bulb, measured in hundreds of hours.

Brand

ABCD

20252423

19232020

21212220

Can we infer that the mean lifetime of the four brands of electric bulbs are equal?