Chi Square Biology

In the formula for chi square, the "o" stands for

• the sum

• the observed frequency

• the expected frequency

• the p value

In the formula for Chi Sqare, the "e" stands for

• the sum

• the observed frequency

• the expected frequency

• the p value

If the calculated chi square value is less than the critical value, then you

• fail to reject the null hypothesis

• cry

• reject the null hypothesis

• go home

What is the null hypothesis (H₀) for the study shown?

• Injury type is independent of position played; there is no significant difference in the distribution of injury type across the positions.

• Injury type is dependent on the position played; there is a significant difference in the distribution of injury type across the positions.

This study is trying to determine if more babies are born on a particular day of the week. How many degrees of freedom would there be for this study?

• 4

• 5

• 6

• 7

The table shows the number or babies born on each day of the week. Is there evidence that births are more likely on specific days of the week?

(You need to do the math to answer this!)

• Yes, the chi square value is less than the critical value and we reject the H₀

• No, the chi square value exceeds the critical value and we fail to reject the H₀

• Yes, the chi square value exceeds the critical value and we reject the H₀

• No, the chi square value is less than the critical value and we fail to reject the H₀

A chi-square test is used to test whether a 1 to 10 spinner is "fair" (that is, the outcomes are all equally likely). The spinner is spun 100 times, and the results are recorded. The degrees of freedom for the test will be

• 8

• 9

• 10

• 99

Recent revenue shortfalls in a midwestern state led to a reduction in the state budget for higher education.  To offset the reduction, the largest state university proposed a 25% tuition increase.  It was determined that such an increase was needed simply to compensate for the lost support from the state.  Separate random samples of 50 freshmen, 50 sophomores, 50 juniors, and 50 seniors from the university were asked whether they were strongly opposed to the increase, given that it was the minimum increase necessary to maintain the university's budget at current levels.  The results are in the table provided.  Why hypotheses would be appropriate for performing a chi-square test?

• The null hypothesis is that the closer students get to graduation, the less likely they are to be opposed to tuition increases.  The alternative is that how close students are to graduation makes no difference in their opinion.
• The null hypothesis is that the mean number of students who are strongly are opposed is the same for each of the 4 years.  The alternative is that the mean is different for at least 2 of the 4 years.
• The null hypothesis is that the distribution of student opinion about the proposed tuition increase is the same for each of the 4 years at the university.  The alternative is that the distribution is different for at least 2 of the 4 years.
• The null hypothesis is that year in school and student opinion about the tuition increase in the sample are independent.  The alternative is that these variables are dependent.

A random sample of traffic tickets given to motorists in a large city is examined. The tickets are classified according to the race of the driver. The results are summarized in the table provided. Assuming H₀ is true, the expected number of Hispanic drivers who would receive a ticket is

• 10

• 9

• 12

• 15

All current-carrying wires produce electro-magnetic (EM) radiation.  High-frequency EM radiation is thought to be a cause of cancer.  The lower frequencies are generally assumed to be harmless.  To investigate the relationship between current configuration and type of cancer, researchers visited the addresses of a random sample of children who died of some form of cancer (leukemia, lymphoma, or some other type) and classified the wiring configuration outside the dwelling as either high-current configuration (HCC) or low-current configuration (LCC).  The data is provided in a table.  Which of the following may we conclude, based on the test results?

• There is convincing evidence of an association between wiring configuration and the chance that a child will develop some form of cancer.
• HCC either causes cancer directly or is a major contributing factor to the development of cancer in children.
• There is not convincing evidence of an association between wiring configuration and the type of cancer that cause the deaths of children in the study.
• There is convincing evidence that HCC does not cause cancer in children.