# choosing the right model

#### floriandotti

##### New Member
Hello,

Does it makes sense to test H_knot : Beta1 = 0 after having rejected H_knot : Beta2 = 0.

So in other words, if it appears that a 2nd order term involving X is useful in fitting a model to the data, does it make sense to test for a simpler model?

why?

thanks

#### Masteras

##### TS Contributor
what is the second term, b1=2 and b2=3 for instance and you rejected b2=0? These two parameters can be tested differently with the t-test if that is what you mean.

#### floriandotti

##### New Member
I mean in a hypothesis test to check to see if a model included b2 is useful.

so it would be

h0: b2 = 0
hA: b2 doesn't equal 0

we reject h0, so it appears that b2 is useful in describing the relationship between x and y.

So know that the model y=b0+b1x1+b2x2 IS indeed useful, does it make sense to check the usefullness of the model y=b0+b1x1?

#### Masteras

##### TS Contributor
is it useful to test y=b0+b2x2 was my initial question?

#### floriandotti

##### New Member
oooh.

haha.

I didn't even think about that. thanks!