Question

5.  In general, when performing Chi-square (goodness-of-fit) on a set of data, what does it mean to fail to reject your null hypothesis?  That is, what does it tell you about your data?  ____________

     __________________________________________________________________________________________

6.  Suppose you must reject your null hypothesis.  What would that mean about your experimental hypothesis? _______________________________________________________________________________

7a.   Based on the c²value, the p-value is determined.  What does a p-value tell you? ______________ __________________________________________________________________________________________

7b.   As c²   increases, the p-value ____________________.

7c.   Assume that Chi-square analysis of experimental data gives a p-value of 0.04.  What does this indicate about the validity of the experimental hypothesis? __________________________________

7d.   Neither a p-value of .30 and of .90 require you to reject your hypothesis.  Which would a researcher prefer to see?  Explain. __________________________________________________________

Table 1	“Monohybrid” Cross
	HH	Hh	hh	Total
Observed (o)				200
Expected (e)				200
Deviation (o-e)
Deviation2 d2
d2/e				c2  =  Σ(d2/e) =

1. State the experimental hypothesis for Problem 1. ____________________________
   _______________________________________

2. Fill in Table 1 with your data (o) and your predictions (e).  

3. Write the ratio of your observed data.

____ HH: ____ Hh: ____hh

4. Complete the table and fill in the c²  value on the bottom row.

5. How many degrees of freedom are there for this problem? _______

6. What is the p–value for this data? _______

7. Does your data support the null hypothesis or must you reject it? _____________________________

8. Does your data support the experimental hypothesis or must you reject it? ___________________

Problem 2:  Genetic Corn

1. State the experimental hypothesis for Problem 2. ___________________________________________
   __________________________________________________________________________________________

2a. Based on the hypothesis, write in the expected phenotypic ratio for the cross cross PpSs X PpSs.

     ______ purple, smooth: _____ purple, wrinkled: _____ yellow, smooth: _____ yellow, wrinkled

2b. Write your calculated ratio below.  

     ______ purple, smooth: _____ purple, wrinkled: _____ yellow, smooth: _____ yellow, wrinkled

3. Complete the Chi-square table below.  The observed are your counts of corn kernels. The expected is based on the phenotypic ratio predicted for the cross.

Table 7	Genetic Corn  (kernel count for 5 rows)
	Purple Smooth	Purple Wrinkled	Yellow Smooth	Yellow Wrinkled	Total
Observed (o)
Expected (e)
Deviation (o-e)
Deviation2 d2
d2/e					c2  =  Σ(d2/e) = ______________

4. How many degrees of freedom are there for this problem? _______

5.  What is the p–value for this data? _______

6.  A p-value equal to or below _______ means that the deviation between observed and expected is too great to be explained by chance, and that you must __________ the hypothesis.

7.  A higher p-value indicates a _____________ fit between observed and expected.

8.  Does the p-value indicate that the data supports the null hypothesis or must you reject it? ______

9.  Does your p-value indicate that your data data supports the experimental hypothesis or must you reject it? ________________

10.   There are 2 possibilities for the location of the genes for kernel color and kernel shape.  Your hypothesis was that the genes are on different pairs of chromosomes and therefore assort independently.  If your data resulted in rejecting this hypothesis, what is the only other possibility for the location of the 2 genes? ____________________________________________________________

11.   Had you done this exercise is a lab room, each team would have counted several rows on different ears of corn.  Why would that improve the likelihood of more statistically reliable results than the method you used? _______________________________________________________________

Answer 1

6. Null hypothesis is rejected of p value is less than 0.05 or 5%.

7a. p value is the probability value that tells us the probability of the relatedness between observed and expected data.

7b. Decreases, there in an inverse relation between chi square value and p value.

7c. If p value is less than 0.05 or 5%, than we reject the null hypothesis. This indicates that the differences present between the observed and expected data are not due to chance and are statistically significant.

7d. It means the null hypothesis has been accepted and the differences present between observed and expected data are only due to chance.

According to guidelines, only first question can be answered.

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