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A student is conducting ascience experiment and wants to test whether you would

ID: 2916470 • Letter: A

Question

A student is conducting ascience experiment and wants to test whether you would have ahigher probability of getting a “heads” or“tails” with a coin flip. To test this, he performs 300trials of 3 coin tosses per trial and records the number of headsin each sequence of 3 tosses. The results are shown in the tablebelow. Is this a fair coin?

NUMBER OF HEADS

0

1

2

3

FREQUENCY

53

125

95

27

We are interested in testing whether the coin is fair. One wayto state the null hypothesis is H0: p = .5, where p isthe probability of heads. Use the probabilities in the table belowto determine the expected count of each number of heads in 300repetitions of 3 tosses.

NUMBER OF HEADS

0

1

2

3

PROBABILITY

.125

.375

.375

.125


expected count of 0 heads in 300 repetitions = 37.5

expected count of 1 head in 300 repetitions = 112.5

expected count of 2 heads in 300 repetitions = 112.5

expected count of 3 heads in 300 repetitions = 37.5

Value of the test statistic for this hypothesis test =13.46

If the significance level is = .05, the cutoff value of therejection region for this hypothesis test = 7.814728

The conclusion is that we should reject the null hypothesis anddetermine the coin is not fair. Considering this, determinethe value of the standardized residual for each of the categories(don't forget to include the "minus" sign if a standardizedresidual is negative; use 4 decimal places).

1. What is the standardized residual for "0 heads" category?(the answer is not .94155 or .9416)
2. What is the standardized residual for "1 head" category?(the answer is not .75932 or .7593)
3. What is the standardized residual for "2 heads" category?(the answer is not -1.06304 or -1.0630)
4. What is the standardized residual for "3 heads" category?(the answer is not -.63783 or -.6378)

NUMBER OF HEADS

0

1

2

3

FREQUENCY

53

125

95

27

Explanation / Answer

The formula to calculate the standardized residual in thissituation is (S) = R/SQRT[V(R)]
Here R can be calculated as follows

Number of times headappears

Observed values

Expected values

Residual(R )=Observed-Expected

0

53

37.5

15.5

1

125

112.5

12.5

2

95

112.5

-17.5

3

27

37.5

-10.5

Variance

271

By using the above standardized formula we have the followingvalues

Number of times headappears

Standardizedresidual

0

0.9415

1

0.7593

2

-1.063

3

-0.6378

The standardized residual for "0 heads" category is 0.94155
The standardized residual for "0 heads" category is 0.7593

The standardized residual for "0 heads" category is-1.063

The standardized residual for "0 heads" category is -0.6378

Number of times headappears

Observed values

Expected values

Residual(R )=Observed-Expected

0

53

37.5

15.5

1

125

112.5

12.5

2

95

112.5

-17.5

3

27

37.5

-10.5



Variance

271