practice.dsc10.com/docs/fa23-quiz3/index.html at 798458e2b9bdce063838165ebf66f5feb4ac6a73 · dsc-courses/practice.dsc10.com · GitHub

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<h1 class="title">Fall 2023 Quiz 3</h1>
</header>
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<p><a href="../index.html">← return to practice.dsc10.com</a></p>
<hr />
<p>This quiz was administered in-person. It was closed-book and
closed-note; students <strong>were not</strong> allowed to use the DSC
10 Reference Sheet. Students had <strong>20 minutes</strong> to work on
the quiz.<br><br>This quiz covered Lectures 14-17 of the <a
href="https://dsc-courses.github.io/dsc10-2023-fa">Fall 2023 offering of
DSC 10</a>.</p>
<hr />
<p><strong>Note (groupby / pandas 2.0):</strong> Pandas 2.0+ no longer
silently drops columns that can’t be aggregated after a
<code>groupby</code>, so code written for older pandas may behave
differently or raise errors. In these practice materials we use
<code>.get()</code> to select the column(s) we want after
<code>.groupby(...).mean()</code> (or other aggregations) so that our
solutions run on current pandas. On real exams you will not be penalized
for omitting <code>.get()</code> when the old behavior would have
produced the same answer.</p>
<hr />
<p>Ciro is an avid fan of Costco, a members-only warehouse store. On his
recent trip to the Morena Boulevard location near campus, he was
surprised by how full shoppers’ carts were and was inspired to
investigate how much people typically spend at Costco.</p>
<hr />
<h2 id="problem-1">Problem 1</h2>
<div class="meta">
<p><span class="pill pill-lecture" title="Lecture number(s)">Lecture
17</span></div></p>
<p>Among all Costco members in San Diego, the average monthly spending
in October 2023 was <strong>$350</strong> with a standard deviation of
<strong>$40</strong>.</p>
<p><br></p>
<h3 id="problem-1.1">Problem 1.1</h3>
<p>The amount Ciro spent at Costco in October 2023 was
<strong>-1.5</strong> in standard units. What is this amount in dollars?
Give your answer as an integer.</p>
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<div class="accordion-item">
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<header id="title-block-header">
<h1 class="title"> </h1>
</header>
<p><strong>Answer</strong>: 290</p>
<hr/>
<h5>Difficulty: ⭐️</h5>
<p>
</p>
<p>The average score on this problem was 93%.</p>
</div>
</div>
</div>
</div>
<p><br></p>
<h3 id="problem-1.2">Problem 1.2</h3>
<p>What is the minimum possible percentage of San Diego members that
spent between <strong>$250</strong> and <strong>$450</strong> in October
2023?</p>
<ul class="task-list">
<li><p><input type="radio" disabled="" /> 16%</p></li>
<li><p><input type="radio" disabled="" /> 22%</p></li>
<li><p><input type="radio" disabled="" /> 36%</p></li>
<li><p><input type="radio" disabled="" /> 60%</p></li>
<li><p><input type="radio" disabled="" /> 78%</p></li>
<li><p><input type="radio" disabled="" /> 84%</p></li>
</ul>
<div id="accordionExample" class="accordion">
<div class="accordion-item">
<h2 class="accordion-header" id="heading1_2">
<button class="accordion-button" type="button" data-bs-toggle="collapse" data-bs-target="#collapse1_2" aria-expanded="true" aria-controls="collapse1_2">
Click to view the solution.
</button>
</h2>
<div id="collapse1_2" class="accordion-collapse collapse"
aria-labelledby="heading1_2" data-bs-parent="#accordionExample">
<div class="accordion-body">
<header id="title-block-header">
<h1 class="title"> </h1>
</header>
<p><strong>Answer</strong>: 84%</p>
<hr/>
<h5>Difficulty: ⭐️⭐️⭐️</h5>
<p>
</p>
<p>The average score on this problem was 61%.</p>
</div>
</div>
</div>
</div>
<p><br></p>
<h3 id="problem-1.3">Problem 1.3</h3>
<p>Now, suppose we’re given that the distribution of monthly spending in
October 2023 for all San Diego members is roughly normal. Given this
fact, fill in the blanks:</p>
<center>
"In October 2023, 95% of San Diego members spent
between __(m)__ dollars and __(n)__ dollars."
</center>
<p><br></p>
<p>What are m and n? Give your answers as integers rounded to the
nearest multiple of 10.</p>
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<div class="accordion-item">
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<div id="collapse1_3" class="accordion-collapse collapse"
aria-labelledby="heading1_3" data-bs-parent="#accordionExample">
<div class="accordion-body">
<header id="title-block-header">
<h1 class="title"> </h1>
</header>
<p><strong>Answer</strong>: m: 270, n: 430</p>
<hr/>
<h5>Difficulty: ⭐️⭐️</h5>
<p>
</p>
<p>The average score on this problem was 81%.</p>
</div>
</div>
</div>
</div>
<p><br></p>
<hr />
<h2 id="problem-2">Problem 2</h2>
<div class="meta">
<p><span class="pill pill-lecture" title="Lecture number(s)">Lecture
15</span></div></p>
<p>Suppose we have access to a simple random sample of all US Costco
members of size <strong>145</strong>. Our sample is stored in a
DataFrame named <code>us_sample</code>, in which the
<code>"Spend"</code> column contains the October 2023 spending of each
sampled member in dollars.</p>
<p><br></p>
<h3 id="problem-2.1">Problem 2.1</h3>
<p>Fill in the blanks:</p>
<center>
"The average of the <code>"Spend"</code> column in <code>us_sample</code> is a ____,
while the average October 2023 spending of all US members is a ____."
</center>
<p><br></p>
<ul class="task-list">
<li><p><input type="radio" disabled="" /> sample statistic; population parameter</p></li>
<li><p><input type="radio" disabled="" /> population statistic; sample parameter</p></li>
<li><p><input type="radio" disabled="" /> sample parameter; population statistic</p></li>
<li><p><input type="radio" disabled="" /> population parameter; sample statistic</p></li>
</ul>
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<div class="accordion-item">
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<button class="accordion-button" type="button" data-bs-toggle="collapse" data-bs-target="#collapse2_1" aria-expanded="true" aria-controls="collapse2_1">
Click to view the solution.
</button>
</h2>
<div id="collapse2_1" class="accordion-collapse collapse"
aria-labelledby="heading2_1" data-bs-parent="#accordionExample">
<div class="accordion-body">
<header id="title-block-header">
<h1 class="title"> </h1>
</header>
<p><strong>Answer</strong>: sample statistic; population parameter</p>
<hr/>
<h5>Difficulty: ⭐️</h5>
<p>
</p>
<p>The average score on this problem was 94%.</p>
</div>
</div>
</div>
</div>
<p><br></p>
<h3 id="problem-2.2">Problem 2.2</h3>
<p>Fill in the blanks below so that <code>us_left</code> and
<code>us_right</code> are the left and right endpoints of a
<strong>46%</strong> confidence interval for the average October 2023
spending of all US members.</p>
<div class="sourceCode" id="cb1"><pre class="sourceCode py"><code class="sourceCode python"><span id="cb1-1"><a href="#cb1-1" aria-hidden="true" tabindex="-1"></a>costco_means <span class="op">=</span> np.array([])</span>
<span id="cb1-2"><a href="#cb1-2" aria-hidden="true" tabindex="-1"></a><span class="cf">for</span> i <span class="kw">in</span> np.arange(<span class="dv">5000</span>):</span>
<span id="cb1-3"><a href="#cb1-3" aria-hidden="true" tabindex="-1"></a>    resampled_spends <span class="op">=</span> __(x)__</span>
<span id="cb1-4"><a href="#cb1-4" aria-hidden="true" tabindex="-1"></a>    costco_means <span class="op">=</span> np.append(costco_means, resampled_spends.mean())</span>
<span id="cb1-5"><a href="#cb1-5" aria-hidden="true" tabindex="-1"></a>left <span class="op">=</span> np.percentile(costco_means, __(y)__)</span>
<span id="cb1-6"><a href="#cb1-6" aria-hidden="true" tabindex="-1"></a>right <span class="op">=</span> np.percentile(costco_means, __(z)__)</span></code></pre></div>
<p>Which of the following could go in blank (x)? <strong>Select all that
apply.</strong></p>
<ul class="task-list">
<li><p><input type="checkbox" disabled="" /> <code>us_sample.sample(145, replace=True).get("Spend")</code></p></li>
<li><p><input type="checkbox" disabled="" /> <code>us_sample.sample(145, replace=False).get("Spend")</code></p></li>
<li><p><input type="checkbox" disabled="" /> <code>np.random.choice(us_sample.get("Spend"), 145)</code></p></li>
<li><p><input type="checkbox" disabled="" /> <code>np.random.choice(us_sample.get("Spend"), 145, replace=True)</code></p></li>
<li><p><input type="checkbox" disabled="" /> <code>np.random.choice(us_sample.get("Spend"), 145, replace=False)</code></p></li>
<li><p><input type="checkbox" disabled="" /> None of the above.</p></li>
</ul>
<p>What goes in blanks (y) and (z)? Give your answers as integers.</p>
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<div id="collapse2_2" class="accordion-collapse collapse"
aria-labelledby="heading2_2" data-bs-parent="#accordionExample">
<div class="accordion-body">
<header id="title-block-header">
<h1 class="title"> </h1>
</header>
<p><strong>Answer</strong>:</p>
<ul>
<li><code>x</code>:
<ul>
<li><code>us_sample.sample(145, replace=True).get("Spend")</code></li>
<li><code>np.random.choice(us_sample.get("Spend"), 145)</code></li>
<li><code>np.random.choice(us_sample.get("Spend"), 145, replace=True)</code></li>
</ul></li>
<li><code>y</code>: <code>27</code></li>
<li><code>z</code>: <code>73</code></li>
</ul>
<hr/>
<h5>Difficulty: ⭐️⭐️</h5>
<p>
</p>
<p>The average score on this problem was 79%.</p>
</div>
</div>
</div>
</div>
<p><br></p>
<h3 id="problem-2.3">Problem 2.3</h3>
<p>True or False: <strong>46%</strong> of all US members in
<code>us_sample</code> spent between <code>left</code> and
<code>right</code> in October 2023.</p>
<ul class="task-list">
<li><p><input type="radio" disabled="" /> True</p></li>
<li><p><input type="radio" disabled="" /> False</p></li>
</ul>
<div id="accordionExample" class="accordion">
<div class="accordion-item">
<h2 class="accordion-header" id="heading2_3">
<button class="accordion-button" type="button" data-bs-toggle="collapse" data-bs-target="#collapse2_3" aria-expanded="true" aria-controls="collapse2_3">
Click to view the solution.
</button>
</h2>
<div id="collapse2_3" class="accordion-collapse collapse"
aria-labelledby="heading2_3" data-bs-parent="#accordionExample">
<div class="accordion-body">
<header id="title-block-header">
<h1 class="title"> </h1>
</header>
<p><strong>Answer</strong>: False</p>
<hr/>
<h5>Difficulty: ⭐️⭐️</h5>
<p>
</p>
<p>The average score on this problem was 85%.</p>
</div>
</div>
</div>
</div>
<p><br></p>
<h3 id="problem-2.4">Problem 2.4</h3>
<p>True or False: If we repeat the code from part (b) 200 times, each
time bootstrapping from a new random sample of 145 members drawn from
all US members, then about <strong>92</strong> of the intervals we
create will contain the average October 2023 spending of all US
members.</p>
<ul class="task-list">
<li><p><input type="radio" disabled="" /> True</p></li>
<li><p><input type="radio" disabled="" /> False</p></li>
</ul>
<div id="accordionExample" class="accordion">
<div class="accordion-item">
<h2 class="accordion-header" id="heading2_4">
<button class="accordion-button" type="button" data-bs-toggle="collapse" data-bs-target="#collapse2_4" aria-expanded="true" aria-controls="collapse2_4">
Click to view the solution.
</button>
</h2>
<div id="collapse2_4" class="accordion-collapse collapse"
aria-labelledby="heading2_4" data-bs-parent="#accordionExample">
<div class="accordion-body">
<header id="title-block-header">
<h1 class="title"> </h1>
</header>
<p><strong>Answer</strong>: True</p>
<hr/>
<h5>Difficulty: ⭐️⭐️⭐️</h5>
<p>
</p>
<p>The average score on this problem was 51%.</p>
</div>
</div>
</div>
</div>
<p><br></p>
<h3 id="problem-2.5">Problem 2.5</h3>
<p>True or False: If we repeat the code from part (b) 200 times, each
time bootstrapping from <code>us_sample</code>, then about
<strong>92</strong> of the intervals we create will contain the average
October 2023 spending of all US members.</p>
<ul class="task-list">
<li><p><input type="radio" disabled="" /> True</p></li>
<li><p><input type="radio" disabled="" /> False</p></li>
</ul>
<div id="accordionExample" class="accordion">
<div class="accordion-item">
<h2 class="accordion-header" id="heading2_5">
<button class="accordion-button" type="button" data-bs-toggle="collapse" data-bs-target="#collapse2_5" aria-expanded="true" aria-controls="collapse2_5">
Click to view the solution.
</button>
</h2>
<div id="collapse2_5" class="accordion-collapse collapse"
aria-labelledby="heading2_5" data-bs-parent="#accordionExample">
<div class="accordion-body">
<header id="title-block-header">
<h1 class="title"> </h1>
</header>
<p><strong>Answer</strong>: False</p>
<hr/>
<h5>Difficulty: ⭐️⭐️⭐️⭐️</h5>
<p>
</p>
<p>The average score on this problem was 30%.</p>
</div>
</div>
</div>
</div>
<p><br></p>
<hr />
<h2 id="section"><span class="math display"> </span></h2>
<h4
id="feedback-find-an-error-still-confused-have-a-suggestion-let-us-know-here.">👋
Feedback: Find an error? Still confused? Have a suggestion?
<a href="https://forms.gle/WZ71FchnXU1K154d7">Let us know
here</u></a>.</h4>
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