Dr. Pagels is a mammalogist who studies meadow and common voles. He frequently t

Question

Dr. Pagels is a mammalogist who studies meadow and common voles. He frequently traps the moles and has noticed what appears to be a preference for a peanut butter-oatmeal mixture by the meadow voles vs apple slices are usually used in traps, where the common voles seem to prefer the apple slices. So he conducted a study where he used a peanut butter-oatmeal mixture in half the traps and the normal apple slices in his remaining traps to see if there was a food preference between the two different voles.

Indicate which of the following is the null hypothesis, and which is the alternate hypothesis.

There food preferences among vole species are independent of one another.
There is a relationship between voles and food preference.

To test for independence, we need to calculate the Chi-square statistic.

These are the data that Dr. Pagels collected:

You will want to use Excel (or Google sheets) to do the calculations for you, so that your answers are exact (they need to be exact to get credit. Here is a Google sheet to get you started.

When transferring your answers, make sure you carry them out to AT LEAST SIX SIGNIFICANT FIGURES unless otherwise stated.

__ = expected meadow vole/apple slices

__-= expected common vole/apple slices

____ = expected meadow vole/peanut butter-oatmeal

___ = expected common vole/peanut butter-oatmeal

___ = chi-square value

___ = degrees of freedom (whole number only)

___= will you reject or fail to reject the null hypothesis? (answer either reject or fail to reject)

Explanation / Answer

ANS-

To calculate the chi square statistic x2 by completing the following steps:

1.    For each observed number in the table subtract the corresponding expected number (O — E).

2.    Square the difference [(O —E)2 ].

3. Divide the squares obtained for each cell in the table by the expected number for that cell [(O - E)2 / E ]

Degree of freedom will be n-1, so n=2

then 2-1 =1 is degree of freedon

To calculate the chi square p value Excel: Steps

Step 1: Calculate your expected value. ...

Step 2: Type your data into columns in Excel. ...

Step 3: Click a blank cell anywhere on the worksheet and then click the “Insert Function” button on the toolbar.

Step 4: Type “Chi” in the Search for a Function box and then click “Go.”

The level of significance depends upon the p value- i.e

The p-value is a number between 0 and 1 and interpreted in the following way: A small p-value (typically 0.05) indicates strong evidence against the null hypothesis, so you reject the null hypothesis.

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