<p style="text-align:justify"><span style="font-size:14px"><strong><span style="color:#002060">EXAMPLE&nbsp;1.21</span></strong></span></p>

<p style="text-align:justify"><span style="font-size:14px"><span style="color:white">Example 1.20</span></span></p>

<p style="text-align:justify"><span style="font-size:14px"><span style="color:black">Researchers want to investigate whether taking aspirin regularly reduces the risk of a heart attack. 400 men between the ages of 50 and 84 are recruited as participants. The men are divided randomly into two groups: one group will take aspirin, and the other group will take a placebo. Each man takes one pill each day for three years, but he does not know whether he is taking aspirin or the placebo. At the end of the study, researchers count the number of men in each group who have had heart attacks.</span></span></p>

<p style="text-align:justify">&nbsp;</p>

<p style="text-align:justify"><span style="font-size:14px"><span style="color:black">Identify the following values for this study: population, sample, experimental units, explanatory variable, response variable, treatments.</span></span></p>

<p>&nbsp;</p>

<p style="text-align:justify"><span style="font-size:14px"><strong><span style="color:#26397f">Solution 1.21</span></strong></span></p>

<p style="text-align:justify">&nbsp;</p>

<p style="text-align:justify"><span style="font-size:14px"><span style="color:black">The </span><strong><em><span style="color:black">population </span></em></strong><span style="color:black">is men aged 50 to 84.</span></span></p>

<p style="text-align:justify"><span style="font-size:14px"><span style="color:black">The </span><strong><em><span style="color:black">sample </span></em></strong><span style="color:black">is the 400 men who participated.</span></span></p>

<p style="text-align:justify"><span style="font-size:14px"><span style="color:black">The </span><strong><em><span style="color:black">experimental units </span></em></strong><span style="color:black">are the individual men in the study.</span></span></p>

<p style="text-align:justify"><span style="font-size:14px"><span style="color:black">The </span><strong><em><span style="color:black">explanatory variable </span></em></strong><span style="color:black">is oral medication.</span></span></p>

<p style="text-align:justify"><span style="font-size:14px"><span style="color:black">The </span><strong><em><span style="color:black">treatments </span></em></strong><span style="color:black">are aspirin and a placebo.</span></span></p>

<p style="text-align:justify"><span style="font-size:14px"><span style="color:black">The </span><strong><em><span style="color:black">response variable </span></em></strong><span style="color:black">is whether a subject had a heart attack.</span></span></p>

<p style="text-align:justify">&nbsp;</p>

<p style="text-align:justify"><span style="font-size:14px"><strong><span style="color:#002060">EXAMPLE&nbsp;1.22</span></strong></span></p>

<p style="text-align:justify">&nbsp;</p>

<p style="text-align:justify"><span style="font-size:14px">The Smell &amp; Taste Treatment and Research Foundation conducted a study to investigate whether smell can affect learning. Subjects completed mazes multiple times while wearing masks. They completed the pencil and paper mazes three times wearing floral-scented masks, and three times with unscented masks. Participants were assigned at random to wear the floral mask during the first three trials or during the last three trials. For each trial, researchers recorded the time it took to complete the maze and the subject&rsquo;s impression of the mask&rsquo;s scent: positive, negative, or neutral.</span></p>

<p style="text-align:justify">&nbsp;</p>

<ol style="list-style-type:lower-alpha">
	<li>
	<p style="text-align:justify"><span style="font-size:14px">Describe the explanatory and response variables in this study.</span></p>
	</li>
	<li>
	<p style="text-align:justify"><span style="font-size:14px">What are the treatments?</span></p>
	</li>
	<li>
	<p style="text-align:justify"><span style="font-size:14px">Identify any lurking variables that could interfere with this study.</span></p>
	</li>
	<li>
	<p style="text-align:justify"><span style="font-size:14px">Is it possible to use blinding in this study?</span></p>
	</li>
</ol>

<p style="text-align:justify">&nbsp;</p>

<p style="text-align:justify"><span style="font-size:14px"><span style="color:#000000"><strong>Solution&nbsp;1.22</strong></span></span></p>

<p style="text-align:justify">&nbsp;</p>

<ol style="list-style-type:lower-alpha">
	<li style="text-align:justify">
	<p><span style="font-size:14px">The explanatory variable is scent, and the response variable is the time it takes to complete the maze.</span></p>
	</li>
	<li style="text-align:justify">
	<p><span style="font-size:14px">There are two treatments: a floral-scented mask and an unscented mask.</span></p>
	</li>
	<li style="text-align:justify">
	<p><span style="font-size:14px">All subjects experienced both treatments. The order of treatments was randomly assigned so there were no differences between the treatment groups. Random assignment eliminates the problem of lurking variables.</span></p>
	</li>
	<li style="text-align:justify">
	<p><span style="font-size:14px">Subjects will clearly know whether they can smell flowers or not, so subjects cannot be blinded in this study. Researchers timing the mazes can be blinded, though. The researcher who is observing a subject will not know which mask is being worn.</span></p>
	</li>
</ol>

<p style="text-align:justify">&nbsp;</p>

<p style="text-align:justify"><span style="font-size:14px"><strong>Example 1.23</strong><span style="color:white"><strong>&nbsp;1.</strong>22</span></span></p>

<p style="text-align:justify">&nbsp;</p>

<p style="text-align:justify"><span style="font-size:14px"><span style="color:black">A researcher wants to study the effects of birth order on personality. Explain why this study could not be conducted as a randomized experiment. What is the main problem in a study that cannot be designed as a randomized experiment?</span></span></p>

<p style="text-align:justify">&nbsp;</p>

<p style="text-align:justify"><span style="font-size:14px"><strong>Solution 1.23</strong></span></p>

<p style="text-align:justify">&nbsp;</p>

<p style="text-align:justify"><span style="font-size:14px"><span style="color:black">The explanatory variable is birth order. You cannot randomly assign a person&rsquo;s birth order. Random assignment eliminates the impact of lurking variables. When you cannot assign subjects to treatment groups at random, there will be differences between the groups other than the explanatory variable.</span></span></p>