# Thread: The following are average weakly losses of worker-hours

1. ## The following are average weakly losses of worker-hours

Question

The following are average weakly losses of worker-hours due to accidents in 10 industrial plants before and after a certain safety program was put in operation :

$

$
$

Use the 0.05 level of significance to test whether the safety program is effective.

2. Originally Posted by zorro
Question

The following are average weakly losses of worker-hours due to accidents in 10 industrial plants before and after a certain safety program was put in operation :

$

$
$

Use the 0.05 level of significance to test whether the safety program is effective.
What have you done? What tests do you know for comparing 'before and after' data?

3. ## I dont know from where to start

Originally Posted by mr fantastic
What have you done? What tests do you know for comparing 'before and after' data?

I dont know where to start , need ur guidance

4. Originally Posted by zorro
I dont know where to start , need ur guidance
But what tests have you learned in class? What do your class notes say? You must have learned tests for this sort of thing otherewise you wouldn't be given questions on it ....

(Personally, without knowing more I'd use a non-parametric test).

5. ## Which test should i use?

Originally Posted by mr fantastic
But what tests have you learned in class? What do your class notes say? You must have learned tests for this sort of thing otherewise you wouldn't be given questions on it ....

(Personally, without knowing more I'd use a non-parametric test).

Should i use the
1) Test concerning the Mean
or
2)Test concerning the difference between the Mean

6. ## Is this correct?

Originally Posted by zorro
Should i use the
1) Test concerning the Mean
or
2)Test concerning the difference between the Mean

I am going to use this please advice me if i am doing it correctly or no !!!

$H_0$ : $\mu_1 - \mu_2$ =0

$H_a$ : $\mu_1 - \mu_2$ < 0

$\alpha$ = 0.05

$
t = \sum_{i=1}^{n} \frac{\bar x_1 - \bar x_2 - 0}{S_p \sqrt{\frac{1}{n_1} + \sqrt{1}{n_2}}}$

where $S_p$ = $\frac{(n_1 - 1)s_1 ^2 + (n_2 - 1) s_2 ^2}{n_1 + n_2 -2}$

7. ## Mr fantastic is this correct???

Originally Posted by mr fantastic
But what tests have you learned in class? What do your class notes say? You must have learned tests for this sort of thing otherewise you wouldn't be given questions on it ....

(Personally, without knowing more I'd use a non-parametric test).

My work

$H_0 : \mu_1 - \mu_2 = 0$
$H_a : | \mu_1 - \mu_2 | > 0$
$\alpha : 0.05$

Since a single tailed $t_{0.05/2 , n_1+ n_2 -1}$ = $t_{0.025,18}$= $2.101$........Is this correct????

$t = \frac{ \bar x - \bar y - 0}{S \sqrt{ \frac{1}{n_1} + \frac{1}{n_2}}}$

where $S^2 = \frac{\sum(x- \bar x)^2 + \sum (y - \bar y)^2}{n_1 + n_2 -2}$= $995.4$...........Is this answer correct????

$\therefore t = 7.26$

since calculate value is 7.26 > 2.101 therefore the $H_0$ is rejected..................Is this procedure for solving the problem correct???