Question :

Samples of two types of electric component were tested for length of life and following data were determined:

$\displaystyle

**\qquad \qquad \qquad \qquad Type1 \qquad \qquad\qquad \qquad Type 2$

$\displaystyle Sample \ size \qquad \qquad n_1 = 8 \qquad \qquad \qquad \qquad n_2 = 7$

$\displaystyle Sample \ mean \qquad \quad \bar{x_1} = 1234 hrs \qquad \qquad \quad \bar{x_2} = 1036 hrs $

$\displaystyle

Sample \ SD's \qquad \quad S_1 = 36 hrs \qquad \qquad \qquad S_2 = 40 hrs

$

Is the difference in means sufficient to say that Type 1 is superior to Type 2 regarding length of life ? State the null hypothesis.