Final answer:
Without specific details of the soccer coach's methodology, it can only be determined that the study was an observational study if the coach simply observed goalies with different gloves, or an experimental study if the gloves were systematically assigned and the variables controlled. Types of sampling are identified as stratified, cluster, and simple random for the given examples.
Step-by-step explanation:
The kind of statistical study the soccer coach may have conducted to determine which brand of gloves is more effective for goalies can be determined by looking at the approach taken. If the coach merely observed his goalkeepers using different brands of gloves during games and practice sessions without controlling any variables or assigning gloves to them in a systematic way, this would be an observational study. However, if the coach assigned different brands to the goalkeepers in a controlled setting and measured performance, then he would have conducted an experimental study. Now, since we don't have specific details on how the coach conducted the study, we cannot be certain. However, a clue may lie in whether the variables were manipulated (experimental study) or simply observed as they naturally occurred (observational study).
To compare, in an experimental study, researchers manipulate one variable to see its effect on another, similar to what an epidemiologist would do in a controlled experiment to measure the effect of room temperature on the spread of the common cold (Figure 1.15). In contrast, an observational study measures characteristics without intervention, much like researchers investigating human biology might use models to observe outcomes without directly interfering with subjects.
The type of sampling used in the examples provided is: (a) stratified sampling, as the players are selected from different age groups, (b) cluster sampling, since all personnel from selected companies are interviewed, and (c) simple random sampling, presuming the teachers were chosen randomly without regard to any specific attributes other than gender.