In an experiment, five rooms were carpeted and five were left uncarpeted. The rooms are similar in size and function. After a suitable period of time, the concentration of bacteria in the air was measured (in units of bacteria per cubic metre) in all of these rooms. The data and summaries are provided:

Based on the analysis above, which of the following is a reasonable conclusion?

A psychologist has developed a set of activities which is intended to help children develop better reading skills. In a study of the effectiveness of these activities, one class of second grade children learns with the activities. Another class of second grade children serves as the control and learns without the activities. After some period of time, the reading skills of all of these children were assessed on a scale of 0 to 100. A summary of these data is:

Do SAT coaching classes work? Do they help students to improve their test scores? Four students were selected randomly from all of the students that completed an SAT coaching class. For each student, we recorded their first SAT score (before the class) and their second SAT score (after the coaching class).

To analyse this data, we should use

Which of the following procedures is extremely sensitive to non-Normal distributions?

DDT is a pesticide banned in Australia for its danger to humans and animals. In an experiment on the impact of DDT, six rats were exposed to DDT poisoning and six rats were not. For each rat in the experiment, a measurement of nerve sensitivity was recorded. The researchers suspected that the mean nerve sensitivity for rats exposed to DDT is greater than that for rats not poisoned. The following data was obtained:

Let 1 be the mean nerve sensitivity for rats poisoned with DDT. Let 2 be the mean nerve sensitivity for rats not poisoned with DDT.

A psychologist has developed a set of activities which is intended to help children develop better reading skills. In a study of the effectiveness of these activities, one class of second grade children learns with the activities. Another class of second grade children serves as the control and learns without the activities. After some period of time, the reading skills of all of these children were assessed. A summary of these data is:

[hint: perform the test of significance and obtain the P-value]

In an experiment, five rooms were carpeted and five were left uncarpeted. The rooms are similar in size and function. After a suitable period of time, the concentration of bacteria in the air was measured (in units of bacteria per cubic metre) in all of these rooms. The data and summaries are provided:

A sports writer wished to see if a football filled with helium travels farther, on average, than a football filled with air. To test this, the writer used 18 adult male volunteers. These volunteers were randomly divided into two groups of nine subjects each. Group 1 kicked a football filled with helium to the recommended pressure. Group 2 kicked a football filled with air to the recommended pressure. The mean distance for group 1 was 30 metres, with a standard deviation s_1 = 8 metres. The mean distance for group 2 was 26 metres, with a standard deviation s_2 = 6 metres. Assume the two groups of kicks are independent. Let \mu_1 and \mu_2 represent the mean distance we would observe for the entire population represented by the volunteers if all members of this population kicked, respectively, a helium- and an air-filled football. Assume that two-sample t-procedures are safe to use.

A psychologist has developed a set of activities which is intended to help children develop better reading skills. In a study of the effectiveness of these activities, one class of second grade children learns with the activities. Another class of second grade children serves as the control and learns without the activities. After some period of time, the reading skills of all of these children were assessed. A summary of these data is:

A psychologist has developed a set of activities intended to help children develop better reading skills. In a study of the effectiveness of these activities, one class of second grade children learns with the activities. Another class of second grade children serves as the control and learns without the activities. After some period of time, the reading skills of all of these children were assessed. A summary of these data is: