Aschool district decides to compare a new math textbook with the textbook that has been used for the past few years. each of the fourth graders in one school is randomly assigned to be in one of two classes, one in which a teacher continues using the old book and another in which a new teacher uses the new book. the school administrators compare the average scores of the two classes on a mathematics standardized test at the end of the year to determine which book is better.

The correct answer for the execise is that teachers have diferent amount of teaching experience and that is a potential confound in the study.

Explanation:

First of all, to conduct a comparison study to a certain dependent variable the researcher has to control all the conditions and only use the dependant condition as the different factor. However in our case, we have one major problem, the teachers should follow the same strategies, same classes, and practically do the same except the book employment. Because the teacher experience can affect the data, the study, the population, and the results. This research is potentially destined to be biased.

answer; the mercertator creation, is the correct answer to the above question; ///good luck

the earth’s crust is broken into separate pieces called tectonic plates (fig. 7.14). recall that the crust is the solid, rocky, outer shell of the planet. it is composed of two distinctly different types of material: the less-dense continental crust and the more-dense oceanic crust. both types of crust rest atop solid, upper mantle material. the upper mantle, in turn, floats on a denser layer of lower mantle that is much like thick molten tar.

each tectonic plate is free-floating and can move independently. earthquakes and volcanoes are the direct result of the movement of tectonic plates at fault lines. the term fault is used to describe the boundary between tectonic plates. most of the earthquakes and volcanoes around the pacific ocean basin—a pattern known as the “ring of fire”—are due to the movement of tectonic plates in this region. other observable results of short-term plate movement include the gradual widening of the great rift lakes in eastern africa and the rising of the himalayan mountain range. the motion of plates can be described in four general patterns:

collision: when two continental plates are shoved together

subduction: when one plate plunges beneath another (fig. 7.15)

spreading: when two plates are pushed apart (fig. 7.15)

transform faulting: when two plates slide past each other (fig. 7.15)