Question :
Samples of two types of electric component were tested for length of life and following data were determined:
Is the difference in means sufficient to say that Type 1 is superior to Type 2 regarding length of life ? State the null hypothesis.
It looks like you are supposed to use a two sample unpaired t-test (because the sample sizes are small) with unequal sample sizes (see Student's t-test - Wikipedia, the free encyclopedia)
The problem with this is that this requires that the distribution of component lives is normal, which is not usually the case and not given in the question.
CB
You can use an F test to determine if the population variances are equal.
If you decide they are, then the test stat for the means is
otherwise you should use Satterthwaite's approximation
http://www.unm.edu/~marcusj/PSE.pdf
which has a typo in it, they squares the pooled sample variance incorrectly in line 11
Could u please provide me with the right solution. If the formula which i have not used is right then which one should i use
In the prev post i asked u if the formula which i used was correct or no , at that time u didnt pointed out this error.....
please let me know what is the right formula and also why , so that i dont make the same mistake again .