Changing the null hypothesis in a t-test












0












$begingroup$


enter image description here



Hello.



I am working on a problem and am confused.



What I know so far is that the two-sided t-test with $alpha=.05$ will reject the null since the $p-$value is smaller.



Here is where I am lost.
The question asks me what to do when the null hypothesis is



$$H_0: mu_1 - mu_2 = 2$$



Intuitively



$$bar{Y_1} - bar{Y_2} = -2$$



so I instantly want to reject the null.
However, I have never seen a situation where the difference between the means are not equal to 0.



How would one approach this problem?










share|cite|improve this question











$endgroup$

















    0












    $begingroup$


    enter image description here



    Hello.



    I am working on a problem and am confused.



    What I know so far is that the two-sided t-test with $alpha=.05$ will reject the null since the $p-$value is smaller.



    Here is where I am lost.
    The question asks me what to do when the null hypothesis is



    $$H_0: mu_1 - mu_2 = 2$$



    Intuitively



    $$bar{Y_1} - bar{Y_2} = -2$$



    so I instantly want to reject the null.
    However, I have never seen a situation where the difference between the means are not equal to 0.



    How would one approach this problem?










    share|cite|improve this question











    $endgroup$















      0












      0








      0





      $begingroup$


      enter image description here



      Hello.



      I am working on a problem and am confused.



      What I know so far is that the two-sided t-test with $alpha=.05$ will reject the null since the $p-$value is smaller.



      Here is where I am lost.
      The question asks me what to do when the null hypothesis is



      $$H_0: mu_1 - mu_2 = 2$$



      Intuitively



      $$bar{Y_1} - bar{Y_2} = -2$$



      so I instantly want to reject the null.
      However, I have never seen a situation where the difference between the means are not equal to 0.



      How would one approach this problem?










      share|cite|improve this question











      $endgroup$




      enter image description here



      Hello.



      I am working on a problem and am confused.



      What I know so far is that the two-sided t-test with $alpha=.05$ will reject the null since the $p-$value is smaller.



      Here is where I am lost.
      The question asks me what to do when the null hypothesis is



      $$H_0: mu_1 - mu_2 = 2$$



      Intuitively



      $$bar{Y_1} - bar{Y_2} = -2$$



      so I instantly want to reject the null.
      However, I have never seen a situation where the difference between the means are not equal to 0.



      How would one approach this problem?







      statistics statistical-inference hypothesis-testing confidence-interval






      share|cite|improve this question















      share|cite|improve this question













      share|cite|improve this question




      share|cite|improve this question








      edited Jan 30 at 20:07







      hyg17

















      asked Jan 30 at 8:50









      hyg17hyg17

      2,00222044




      2,00222044






















          1 Answer
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          $begingroup$

          Define $Y_3:=Y_2-2$ so the null hypothesis is $mu_1=mu_3,,mu_3:=bar{Y}_3$. Note that subtracting $2$ from one variable shifts its mean while leaving the standard deviation and mean's standard error unchanged. Now you can use an equal-means test.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Thank you! So, would it mean that the confidence interval would shift 2 units as well?
            $endgroup$
            – hyg17
            Jan 31 at 19:06










          • $begingroup$
            @hyg17 Yes, when you go from the interval for $mu_1-mu_3$ to that of $mu_1-mu_2$.
            $endgroup$
            – J.G.
            Jan 31 at 22:38












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          1 Answer
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          active

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          1












          $begingroup$

          Define $Y_3:=Y_2-2$ so the null hypothesis is $mu_1=mu_3,,mu_3:=bar{Y}_3$. Note that subtracting $2$ from one variable shifts its mean while leaving the standard deviation and mean's standard error unchanged. Now you can use an equal-means test.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Thank you! So, would it mean that the confidence interval would shift 2 units as well?
            $endgroup$
            – hyg17
            Jan 31 at 19:06










          • $begingroup$
            @hyg17 Yes, when you go from the interval for $mu_1-mu_3$ to that of $mu_1-mu_2$.
            $endgroup$
            – J.G.
            Jan 31 at 22:38
















          1












          $begingroup$

          Define $Y_3:=Y_2-2$ so the null hypothesis is $mu_1=mu_3,,mu_3:=bar{Y}_3$. Note that subtracting $2$ from one variable shifts its mean while leaving the standard deviation and mean's standard error unchanged. Now you can use an equal-means test.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Thank you! So, would it mean that the confidence interval would shift 2 units as well?
            $endgroup$
            – hyg17
            Jan 31 at 19:06










          • $begingroup$
            @hyg17 Yes, when you go from the interval for $mu_1-mu_3$ to that of $mu_1-mu_2$.
            $endgroup$
            – J.G.
            Jan 31 at 22:38














          1












          1








          1





          $begingroup$

          Define $Y_3:=Y_2-2$ so the null hypothesis is $mu_1=mu_3,,mu_3:=bar{Y}_3$. Note that subtracting $2$ from one variable shifts its mean while leaving the standard deviation and mean's standard error unchanged. Now you can use an equal-means test.






          share|cite|improve this answer









          $endgroup$



          Define $Y_3:=Y_2-2$ so the null hypothesis is $mu_1=mu_3,,mu_3:=bar{Y}_3$. Note that subtracting $2$ from one variable shifts its mean while leaving the standard deviation and mean's standard error unchanged. Now you can use an equal-means test.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Jan 30 at 20:12









          J.G.J.G.

          32.6k23250




          32.6k23250












          • $begingroup$
            Thank you! So, would it mean that the confidence interval would shift 2 units as well?
            $endgroup$
            – hyg17
            Jan 31 at 19:06










          • $begingroup$
            @hyg17 Yes, when you go from the interval for $mu_1-mu_3$ to that of $mu_1-mu_2$.
            $endgroup$
            – J.G.
            Jan 31 at 22:38


















          • $begingroup$
            Thank you! So, would it mean that the confidence interval would shift 2 units as well?
            $endgroup$
            – hyg17
            Jan 31 at 19:06










          • $begingroup$
            @hyg17 Yes, when you go from the interval for $mu_1-mu_3$ to that of $mu_1-mu_2$.
            $endgroup$
            – J.G.
            Jan 31 at 22:38
















          $begingroup$
          Thank you! So, would it mean that the confidence interval would shift 2 units as well?
          $endgroup$
          – hyg17
          Jan 31 at 19:06




          $begingroup$
          Thank you! So, would it mean that the confidence interval would shift 2 units as well?
          $endgroup$
          – hyg17
          Jan 31 at 19:06












          $begingroup$
          @hyg17 Yes, when you go from the interval for $mu_1-mu_3$ to that of $mu_1-mu_2$.
          $endgroup$
          – J.G.
          Jan 31 at 22:38




          $begingroup$
          @hyg17 Yes, when you go from the interval for $mu_1-mu_3$ to that of $mu_1-mu_2$.
          $endgroup$
          – J.G.
          Jan 31 at 22:38


















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