Is This What P Means? A randomized comparative experiment examined the effect of the attractiveness of an instructor on the performance of students on a quiz given by the instructor. The researchers found a statistically significant difference in quiz scores between students in a class with an instructor rated as attractive and students in a class with an instructor rated as unattractive (P = 0.005).8 When asked to explain the meaning of "p = 0.005," a student says, "This means there is only probability of 0.005 that the null hypothesis is true." Explain what P = 0.005 really means in a way that makes it clear that the student's explanation is wrong.

questions are not graded.

Studies indicate that excessive noise at night can affect weight gain. One study of n = 127 rats compared the weight gain of rats exposed to excessive noise at night and the weight gain of rats in a quiet night environment. Sample statistics for the study are given in the table below. Use this information to determine if there is significant evidence that weight gain of rats exposed to excessive noise at night is different on average than weight gain of rats in a quiet night environment.        Excessive noise at night environment  (Group 1)   Quiet night environment  (Group 2) Sample mean (grams) 22.4 19.9 Sample standard deviation (grams) 6.4 3.8 Observations/Sample size 69 58       Is this a one-tailed or a two-tailed test? Explain in one or two sentences.

In a population of 150 pea plants, there are 89 tall-purple plants, 25 short-purple plants, 28 tall-white plants, and 8 short-white plants. In order to test if the two traits are experiencing independent assortment researchers would perform a chi squared test.   What is your calculated Chi Squared statistic? What is the corresponding P value?

A graduate student is interested in how viewing different types of scenes affects working memory. For his study, he selects a random sample of 36 adults. The subjects complete a series of working memory tests before and after walking in an urban setting. Before the walk, the mean score on the test of working memory was 9.1. After the walk, the mean score was 1.4 higher. The graduate student has no presupposed assumptions about how viewing different types of scenes affects working memory, so he formulates the null and alternative hypotheses as: H00 : μDD = 0 H11 : μDD ≠ 0 Assume that the data satisfy all of the required assumptions for a repeated-measures t test. The graduate student calculates the following statistics for his hypothesis test: Mean difference (MDD) 1.4 Estimated population standard deviation of the differences (s) 1.6 Estimated standard error of the mean differences (sMDMD) 0.2667 Degrees of freedom (df) 35 The t statistic 5.25 The critical values of t…

A researcher gathered a sample of participants who volunteered for a studying of phobias. She measured anxiety level of participants as they viewed photos of spiders and again when they viewed puppies. Which statistical test is appropriate for this study and why?

Researchers investigate how the presence of cell phones influence the quality of human interaction.  Subjects are randomly selected from a population and divided into an experimental group that is asked to leave their phones in the front of the room and a control group that are not asked to leave their cell phones at the front of the room.  Subjects are left alone for 10 minutes and then asked to take a survey designed to measure quality of interactions they had with others in the experiment.  What statistical test is appropriate?

A Michigan study concerning preference for outdoor activities used a questionnaire with a six-point Likert-type response in which 1 designated "not important" and 6 designated "extremely important." A random sample of n1 = 44 adults were asked about fishing as an outdoor activity. The mean response was x1 = 4.9. Another random sample of n2 = 49 adults were asked about camping as an outdoor activity. For this group, the mean response was x2 = 4.1. From previous studies, it is known that ?1 = 1.5 and ?2 = 2.0. Does this indicate a difference (either way) regarding preference for camping versus preference for fishing as an outdoor activity? Use a 5% level of significance. Note: A Likert scale usually has to do with approval of or agreement with a statement in a questionnaire. For example, respondents are asked to indicate whether they "strongly agree," "agree," "disagree," or "strongly disagree" with the statement.

Is the proportion of wildfires caused by humans in the south different from the proportion of wildfires caused by humans in the west? 350 of the 519 randomly selected wildfires looked at in the south were caused by humans while 383 of the 500 randomly selected wildfires looked at the west were caused by humans. What can be concluded at the a = 0.01 level of significance? Rectangular Snip a. For this study, we should use Select an answer b. The null and alternative hypotheses would be: Ho: Select an answer | (please enter a decimal) Select an answer v Select an answer H1: Select an answer v Select an answer vSelect an answer v (Please enter a decimal) c. The test statistic ? v = (please show your answer to 3 decimal places.)

In a study examining the relation of math ability to the belief that math ability was innate, the belief was considered the predictor variable. The researcher hopes to find a correlation between the participants’ math ability and their belief that math ability is innate.  The scores for the three participants are shown below.   The group that believed that math is NOT innate scored 66, 70, 50.   The group that believed that math IS innate scored 7, 4,10.                                Calculate, by hand, the correlation between these two variables.  Is it positive or negative and is it a strong correlation?