To conduct a runs test on a sample, perform the following steps:

The appropriate formula for the test of hypothesis depends on the sample size. The formulas are shown below and are identical to those we presented for estimating the mean of a single sample presented (e.g., when comparing against an external or historical control), except here we focus on difference scores.

An Application: Suppose we wish to test the null hypothesis

“Testing the Two-Step Flow of Communication Hypothesis.” InInsights Into Consumer Behavior.


We now substitute the sample data into the formula for the test statistic identified in Step 2. Before substituting, we will first compute Sp, the pooled estimate of the common standard deviation.

“We would urge that the Katz- Lazarsfeld two-step flow hypothesis, ..

Again, the χ2 test of independence is used to test whether the distribution of the outcome variable is similar across the comparison groups. Here we rejected H0 and concluded that the distribution of exercise is not independent of living arrangement, or that there is a relationship between living arrangement and exercise. The test provides an overall assessment of statistical significance. When the null hypothesis is rejected, it is important to review the sample data to understand the nature of the relationship. Consider again the sample data.

We now substitute the sample data into the formula for the test statistic identified in Step 2.

A revision of the two-step flow of communications hypothesis

Consider again the NCHS-reported mean total cholesterol level in 2002 for all adults of 203. Suppose a new drug is proposed to lower total cholesterol. A study is designed to evaluate the efficacy of the drug in lowering cholesterol. Fifteen patients are enrolled in the study and asked to take the new drug for 6 weeks. At the end of 6 weeks, each patient's total cholesterol level is measured and the sample statistics are as follows: n=15, x̄ =195.9 and s=28.7. Is there statistical evidence of a reduction in mean total cholesterol in patients after using the new drug for 6 weeks? We will run the test using the five-step approach.


Or, it might be that we would have to go backseveral steps before we found the link between the interpersonal networks ofpublic affairs opinion and disproportionate mass media ef­fect Compared withthe realm of fashions at any rate, one is led to suspect that the chain ofinterpersonal influence is longer in the realm of public affairs and that"inside dope" as well as influencing in specific influence episodesis much more a person-to-person affair.

As aresult of these find­ings, the idea of the "two-step flow ofcommunication" gains credence.

what is two-step flow of communication

In this example, we have one sample and a discrete (ordinal) outcome variable (with three response options). We specifically want to compare the distribution of responses in the sample to the distribution reported the previous year (i.e., 60%, 25%, 15% reporting no, sporadic and regular exercise, respectively). We now run the test using the five-step approach.

We now substitute the sample data into the formula for the test statistic identified in Step 2.

05/01/2018 · Two-step flow of communication A

The second statement indicates that if two events, A and B, are independent then the probability of their intersection can be computed by multiplying the probability of each individual event. To conduct the χ2 test of independence, we need to compute expected frequencies in each cell of the table. Expected frequencies are computed by assuming that the grouping variable and outcome are independent (i.e., under the null hypothesis). Thus, if the null hypothesis is true, using the definition of independence:

that the two-step flow hypothesis claims ..

This example raises an important issue in terms of study design. In this example we assume in the null hypothesis that the mean cholesterol level is 203. This is taken to be the mean cholesterol level in patients without treatment. Is this an appropriate comparator? Alternative and potentially more efficient study designs to evaluate the effect of the new drug could involve two treatment groups, where one group receives the new drug and the other does not, or we could measure each patient's baseline or pre-treatment cholesterol level and then assess changes from baseline to 6 weeks post-treatment. These designs are also discussed here.