An engineer living at an elevation of $2500 \mathrm{ft}$ is conducting experiments to verify predictions of glider performance. To process data, the density of ambient air is needed. The engineer measures temperature $\left(74.3^{\circ} \mathrm{F}\right)$ and atmospheric pressure $(27.3$ inches of mercury). Compute density in units of $\mathrm{kg} / \mathrm{m}^3$. Compare the calculated value with data from the mentioned table and make a recommendation about the effects of elevation on density; that is, are the effects of elevation significant?

Performance Bike Co. is a wholesaler of motorcycle supplies. An aging of the company's accounts receivable on December 31 and a historical analysis of the percentage of uncollectible accounts in each age category are as follows:

$$\begin{array}{lrc} \text { Age Interval } & \text { Balance } & \begin{array}{c} \text { Percent } \\ \text { Uncollectlble } \end{array} \\ \hline \text { Not past due } & \$ 3,250,000 & 0.8 \% \\ 1-30 \text { days past due } & 1,050,000 & 2.4 \\ 31-60 \text { days past due } & 780,000 & 7.0 \\ 61-90 \text { days past due } & 320,000 & 18.0 \\ 91-180 \text { days past due } & 240,000 & 34.0 \\ \text { Over } 180 \text { days past due } & \underline{\hspace{15pt}150,000} & 85.0\\ &\underline{\underline{\$5,790,000}} \end{array}$$

Assume that the allowance for doubtful accounts for Performance Bike Co. had a debit balance of $28,400 as of December 31.

Journalize the adjusting entry for uncollectible accounts as of December 31.

Suppose a Brayton engine is run as a refrigerator. In this case, the cycle begins at temperature $T_1$, and the gas is isobarically expanded until it reaches temperature $T_4$. Then the gas is adiabatically compressed, until its temperature is $T_{3^{-}}$. It is then isobarically compressed, and the temperature changes to $T_2$. Finally, it is adiabatically expanded until it returns to temperature $T_1$. a) Sketch this cycle on a $p V$-diagram. b) Show that the coefficient of performance of the engine is given by $K=\left(T_4-T_1\right) /\left(T_3-T_2-T_4+T_1\right)$.

(a) Give two original examples of time series data.

(b) Give two original examples of crosssectional data. In each case, identify the unit of observation carefully. If the data are both crosssectional and time series, explain why. Hint: Do not restrict yourself to published data, and consider data describing your own life (e.g., sports performance or financial data). You need not list any data, merely describe them and perhaps show a few typical data values.

Performance of stock screeners. Refer to the American Association of Individual Investors (AAII) statistics on stock screeners, Exercise $2.44$ (p. 71). Annualized percentage return on investment (as compared to the Standard & Poor's 500 Index) for 13 randomly selected stock screeners are reproduced in the table. Find the range of the data for the 13 stock screeners. Give the units of measurement for the range.

$9.0$	$-.1$	$-1.6$	$14.6$	$16.0$	$7.7$	$19.9$	$9.8$	$3.2$	$24.8$	$17.6$	$10.7$	$9.1$

The following data pertain to the Waikiki Sands Hotel for the month of March.

$$\begin{array}{lcc} & \textbf{ Flexible Budget March } & \textbf{ Actual Results March } \\ & \textbf{ (in thousands)* } & \textbf{ (in thousands)* } \\ \text{ Banquets and Catering } & \$ 650 & \$ 658 \\ \text{ Restaurants } & 1,800 & 1,794 \\ \text{ Kitchen staff wages } & (85) & (86) \\ \text{ Food } & (690) & (690) \\ \text{ Paper products } & (125) & (122) \\ \text{ Variable overhead } & (75) & (78) \\ \text{ Fixed overhead } & (90) & (93) \end{array}$$

$^*$Numbers without parentheses denote profit; numbers with parentheses denote expenses.

Prepare a March performance report. The report should have six numerical columns with headings analogous. Your performance report should cover only the Food and Beverage Department and the Kitchen. Draw arrows to show the relationships between the numbers in the report. For the year-to-date columns in your report, use the previous data given. You will need to update those figures using the March data given above.

The following selected accounts appear in Shaw Company's unadjusted trial balance at December 31, 2018, the end of its fiscal year (all accounts have normal balances).

$$\begin{array}{lrlr} \text{ Prepaid advertising }& \$ 1,200 &\text{ Performance obligations }& \$ 5,400 \\ \text{ Wages expense }& 43,800 &\text{ Service fees revenue }& 87,000 \\ \text{ Prepaid insurance }& 3,420 &\text{ Rental income }& 4,900 \\ \end{array}$$

Prepare its adjusting entries at December 3 I. 2018. (1) using the financial statement effects template. and (2) in journal entry form using the following additional information.

1. Prepaid advertising at December 31 is $800.
2. Unpaid and unrecorded wages earned by employees in December are$1,300.
3. Prepaid insurance at December 31 is $2,280.
4. Perfomance obligations represent service fees collected in advance of when the services are provided to customers. Performance obligations at December 31 are$3,000.
5. Rent revenue of$ 1,000 owed by a tenant is not recorded at December 31 .

True or false: (a) Work can never be converted completely into heat. (b) Heat can never be converted completely into work. (c) All heat engines have the same efficiency. (d) It is impossible to transfer a given quantity of heat from a cold reservoir to a hot reservoir. (e) The coefficient of performance of a refrigerator cannot be greater than 1. (j) All Carnot engines are reversible. (g) The entropy of a system can never decrease. (h) The entropy of the universe can never decrease.

Cell Design produces cell phone covers for all makes and models of cell phones. Cell Design sells 1,050,000 units each year at a price of $10 per unit and a contribution margin of 40%.

A survey of Cell Design customers over the past 12 months indicates that customers were very satisfied with the products but a disturbing number of customers were disappointed because the products they purchased did not fit their phones. They then had to hassle with returns and replacements.

Cell Design’s managers want to modify their production processes to develop products that more closely match Cell Design’s specifications because the quality control in place to prevent ill-fitting products from reaching customers is not working very well.

The current costs of quality are as follows:

$$\begin{array}{lr} \text{Prevention costs}& \$210,000\\ \text{Appraisal costs}& \$100,000\\ \text{Internal failure costs}&\\ \quad\text{Rework}& \$420,000\\ \quad\text{Scrap}& \$ 21,000\\ \text{External failure costs}&\\ \quad\text{Product replacements}& \$315,000\\ \quad\text{Lost sales from customer returns}& \$787,500\\ \text{The QC manager and controller have forecast the following}& \\ \quad\text{additional costs to modify the production process.}&\\ \text{CAD design improvement}& \$150,000\\ \text{Improve machine calibration to specifications}& \$137,500\\ \end{array}$$

1. Which cost of quality category are managers focusing on? Why?

2. If the improvements result in a 60% decrease in customer replacement cost and a 70% decrease in customer returns, what is the impact on the overall COQ and the company’s operating income? What should Cell Design do? Explain.

3. Calculate prevention, appraisal, internal failure, and external failure costs as a percentage of total quality costs and as a percentage of sales before and after the change in the production process. Comment briefly on your results.

The following performance scores have been recorded for 25 job applicants who have taken a preemployment aptitude test administered by the company to which they applied:

$$\begin{array}{rrrrrrrrr}66.6 & 75.4 & 66.7 & 59.2 & 78.5 & 80.8 & 79.9 & 87.0 & 94.1 \\ 70.2 & 92.8 & 86.9 & 92.8 & 66.8 & 65.3 & 100.8 & 76.2 & 87.8 \\ 71.0 & 92.9 & 97.3 & 82.5 & 78.5 & 72.0 & 76.2 & & \end{array}$$

Construct a frequency distribution and a histogram for these data.

In 2012, the New York Yankees won 95 games and spent $\$ 198$ million on salaries for their players (USA Today). Is there a relationship between salary and team performance in Major League Baseball? For the 2012 season, a linear model fit to the number of Wins (out of 162 regular season games) from the team Salary $(\$ M)$ for the 30 teams in the league is:

$$\widehat{\text { Wins }}=76.45+0.046 \text { Salary. }$$

c) What does the slope mean in this context?

Performance data for a centrifugal fan of 3-ft diameter tested at 750 rpm are $$ \begin{matrix}\text{Volume flow} & \text{106} & \text{141} & \text{176}\\\mathrm{rate, Q (ft^{3}/s)}\\\text{Static pressure} & \text{0.075} & \text{0.073} & \text{0.064}\\\mathrm{rise, \Delta p (psi)}\\\text{Power output,} & \text{2.75} & \text{3.18} & \text{3.50}\\\mathrm{\scr{P} (hp)}\\\text{Volume flow} & \text{211} & \text{246} & \text{282}\\\mathrm{rate, Q (ft^{3}/s)}\\\text{Static pressure} & \text{0.050} & \text{0.033} & \text{0.016}\\\mathrm{rise, \Delta p (psi)}\\\text{Power output,} & \text{3.51} & \text{3.50} & \text{3.22}\\\mathrm{\scr{P} (hp)}\\\end{matrix} $$ Plot the performance data versus volume flow rate. Calculate static efficiency, and show the curve on the plot. Find the best efficiency point, and specify the fan rating at this point.

Explain why the following technique for transaction execution may provide better performance than just using strict two-phase locking: First execute the transaction without acquiring any locks and without performing any writes to the database as in the validation-based techniques, but unlike the validation techniques do not perform either validation or writes on the database. Instead, rerun the transaction using strict two-phase locking. (Hint: Consider waits for disk I/O.)

In a poll conducted by The New York Times and CBS News, $44 \%$ of Americans approve of the job that the Supreme Court is doing (The New York Times, June 8, 2012). Assume that at the time of the poll, this percentage applied to the entire American population. A recent survey of 1300 Americans found that $39\%$ of them are satisfied with the Supreme Court's performance. Can you draw the conclusion that the present percentage of Americans who approve of the job the Supreme Court is doing is different from $.44$ at a significance level of $2\%$t?