Comments on: Miss Loi In Hostage Crisis! http://www.exampaper.com.sg/questions/e-maths/miss-loi-in-hostage-crisis Sassy O Level Maths Tuition, Questions & Tips from Singapore's Favourite Private Tutor Sun, 05 Feb 2012 17:08:39 +0000 hourly 1 By: Last-Minute Buddha Foot Hugging Words | Jφss Sticks | Diary of a Private O Level Maths Tutor in Singapore http://www.exampaper.com.sg/questions/e-maths/miss-loi-in-hostage-crisis#comment-14943 Last-Minute Buddha Foot Hugging Words | Jφss Sticks | Diary of a Private O Level Maths Tutor in Singapore Tue, 21 Oct 2008 10:48:23 +0000 http://www.exampaper.com.sg/questions/e-maths/miss-loi-in-hostage-crisis#comment-14943 [...] that you know which buttons (e.g. DATA, σn etc.) to use in YOUR calculator for mean and standard deviation [...] [...] that you know which buttons (e.g. DATA, σn etc.) to use in YOUR calculator for mean and standard deviation [...]

]]> By: clarion-x http://www.exampaper.com.sg/questions/e-maths/miss-loi-in-hostage-crisis#comment-13276 clarion-x Tue, 09 Sep 2008 11:24:52 +0000 http://www.exampaper.com.sg/questions/e-maths/miss-loi-in-hostage-crisis#comment-13276 Heheh... No lah. Full marks for EM trigo! XD (however the same feat could, unfortunately, not be repeated for AM. le sigh...) Heheh... No lah. Full marks for EM trigo! XD

(however the same feat could, unfortunately, not be repeated for AM. le sigh...)

]]> By: Miss Loi http://www.exampaper.com.sg/questions/e-maths/miss-loi-in-hostage-crisis#comment-13202 Miss Loi Sun, 07 Sep 2008 15:43:17 +0000 http://www.exampaper.com.sg/questions/e-maths/miss-loi-in-hostage-crisis#comment-13202 <b>Kenny:</b> Bright spotlights and camera flashes make me dizzy :P Thanks <b>Soupie</b> + <b>Daniel</b> + <b>ECL</b>. Finally finished the <a href="/miss-loi-the-tutor/the-stressed-owner-of-the-best-blog-shop-at-the-spore-blog-awards" rel="nofollow">write-up on Friday's event</a>. A pity they held it on one of Miss Loi's busiest weekends of the entire year *tired* <b>Clarion:</b> Good things in life must share <i>mah</i> ;) Hope you didn't enjoy until you've forgotten all your formulae when school re-opens tomorrow! Kenny: Bright spotlights and camera flashes make me dizzy :P

Thanks Soupie + Daniel + ECL. Finally finished the write-up on Friday's event. A pity they held it on one of Miss Loi's busiest weekends of the entire year *tired*

Clarion: Good things in life must share mah ;) Hope you didn't enjoy until you've forgotten all your formulae when school re-opens tomorrow!

]]> By: clarion-x http://www.exampaper.com.sg/questions/e-maths/miss-loi-in-hostage-crisis#comment-13188 clarion-x Sun, 07 Sep 2008 04:14:09 +0000 http://www.exampaper.com.sg/questions/e-maths/miss-loi-in-hostage-crisis#comment-13188 wow. err... very honoured to be mentioned in your post. wow. err... very honoured to be mentioned in your post.

]]> By: eastcoastlife http://www.exampaper.com.sg/questions/e-maths/miss-loi-in-hostage-crisis#comment-13165 eastcoastlife Sat, 06 Sep 2008 11:32:03 +0000 http://www.exampaper.com.sg/questions/e-maths/miss-loi-in-hostage-crisis#comment-13165 Congrats Miss Loi on your win! Congrats Miss Loi on your win!

]]> By: Daniel http://www.exampaper.com.sg/questions/e-maths/miss-loi-in-hostage-crisis#comment-13164 Daniel Sat, 06 Sep 2008 11:08:08 +0000 http://www.exampaper.com.sg/questions/e-maths/miss-loi-in-hostage-crisis#comment-13164 Congratulations Ms Loi on the Omy S'pore Blog Awards :) Congratulations Ms Loi on the Omy S'pore Blog Awards :)

]]> By: ignorantsoup http://www.exampaper.com.sg/questions/e-maths/miss-loi-in-hostage-crisis#comment-13155 ignorantsoup Sat, 06 Sep 2008 04:12:52 +0000 http://www.exampaper.com.sg/questions/e-maths/miss-loi-in-hostage-crisis#comment-13155 Miss Loi!! You're on the news again for the Omy blog awards..lol.. congrats, btw, abit slow but better late than never! Miss Loi!! You're on the news again for the Omy blog awards..lol.. congrats, btw, abit slow but better late than never!

]]> By: Miss Loi http://www.exampaper.com.sg/questions/e-maths/miss-loi-in-hostage-crisis#comment-13109 Miss Loi Fri, 05 Sep 2008 17:39:44 +0000 http://www.exampaper.com.sg/questions/e-maths/miss-loi-in-hostage-crisis#comment-13109 Lastly, even though Bobo has a slightly lower mean (i.e. better accuracy but not by much) than Pa Jiao, Bobo's much higher standard deviation means that his shooting consistency is abysmal i.e. he probably has trembling hands and his shots are all over the place. Miss Loi would rather trust Pa Jiao's relatively steadier hands! *Signals to Corporal Pa Jiao and quickly ducks head down by ~40mm* *Bullet is fired and burnt a hole straight through Miss Loi's big aunty hairstyle to hit the robber's gun off his hand* Miss Loi has been saved by Pa Jiao's shot! <div class="superbig center">劇終</div> Lastly, even though Bobo has a slightly lower mean (i.e. better accuracy but not by much) than Pa Jiao, Bobo's much higher standard deviation means that his shooting consistency is abysmal i.e. he probably has trembling hands and his shots are all over the place.

Miss Loi would rather trust Pa Jiao's relatively steadier hands!

*Signals to Corporal Pa Jiao and quickly ducks head down by ~40mm*

*Bullet is fired and burnt a hole straight through Miss Loi's big aunty hairstyle to hit the robber's gun off his hand*

Miss Loi has been saved by Pa Jiao's shot!

劇終
]]> By: Miss Loi http://www.exampaper.com.sg/questions/e-maths/miss-loi-in-hostage-crisis#comment-13108 Miss Loi Fri, 05 Sep 2008 17:24:54 +0000 http://www.exampaper.com.sg/questions/e-maths/miss-loi-in-hostage-crisis#comment-13108 Alright <b>Naomi</b>, time to 'shoot' you now since there wasn't time in class just now :) You answers are spot-on but how did you arrive at your answers? Did you do it the old-fashioned way i.e. Bobo's Mean <m>overline{x}_1 = {47+9+1+4+60+100}/6 = 36.8</m>mm Pa jiao's Mean <m>overline{x}_2 = {32+35+47+39+40+45}/6 = 39.7</m>mm For the standard deviations, you plot out the good o' table and calculate the values one by one: <table> <tr> <th colspan="2">BoBo</th><th colspan="2">Pa Jiao</th> </tr> <tr> <td><var>x</var><sub>1</sub></td> <td><m>(x_1 - overline{x}_1)^2</m></td> <td><var>x</var><sub>2</sub></td> <td><m>(x_2 - overline{x}_2)^2</m></td> </tr> <tr> <td>47</td><td>103.4</td><td>52</td><td>58.8</td> </tr> <tr> <td>9</td><td>774.7</td><td>35</td><td>21.8</td> </tr> <tr> <td>1</td><td>1284</td><td>47</td><td>53.8</td> </tr> <tr> <td>4</td><td>1078</td><td>39</td><td>0.444</td> </tr> <tr> <td>60</td><td>546.7</td><td>40</td><td>0.111</td> </tr> <tr> <td>100</td><td>3990</td><td>45</td><td>28.4</td> </tr> <tr> <td><m>Sigma (x_1 - overline{x}_1)^2 = </m></td><td>7766.83</td><td><m>Sigma (x_2 - overline{x}_2)^2 = </m></td><td>163.33</td> </tr> </table> ∴ Bobo's standard deviation σ<sub>1</sub> = <m>sqrt{{Sigma (x_1 - overline{x}_1)^2}/n} = sqrt{7766.83/6} = 36.0</m>mm ∴ Pa Jiao's standard deviation σ<sub>2</sub> = <m>sqrt{{Sigma (x_2 - overline{x}_2)^2}/n} = sqrt{163.33/6} = 5.2</m>mm <strong>OR</strong> You simply set your super duper calculator to SD <span class="calc-button">MODE</span> and for BoBo: 47 <span class="calc-button">DATA</span> 9 <span class="calc-button">DATA</span> 1 <span class="calc-button">DATA</span> 4 <span class="calc-button">DATA</span> 60 <span class="calc-button">DATA</span> 100 <span class="calc-button">DATA</span> To get Bobo's mean you press <span class="calc-button">x</span> (the one with the <m>overline{x}</m>) on your calculator. To get Bobo's standard deviation you press <span class="calc-button">σn</span> on your calculator. <span class="calc-button">SCR</span> CLEAR your data before repeating the above steps for Pa Jiao. Which method do you think is faster and safer - especially for straightforward <em>non-grouped</em> (i.e. no frequencies) data like the ones in this question? N.B. Once again, actual buttons might differ in your specific calculator model. Alright Naomi, time to 'shoot' you now since there wasn't time in class just now :)

You answers are spot-on but how did you arrive at your answers? Did you do it the old-fashioned way i.e.

Bobo's Mean overline{x}_1 = {47+9+1+4+60+100}/6 = 36.8mm

Pa jiao's Mean overline{x}_2 = {32+35+47+39+40+45}/6 = 39.7mm

For the standard deviations, you plot out the good o' table and calculate the values one by one:

BoBo Pa Jiao
x1 (x_1 - overline{x}_1)^2 x2 (x_2 - overline{x}_2)^2
47 103.4 52 58.8
9 774.7 35 21.8
1 1284 47 53.8
4 1078 39 0.444
60 546.7 40 0.111
100 3990 45 28.4
Sigma (x_1 - overline{x}_1)^2 = 7766.83 Sigma (x_2 - overline{x}_2)^2 = 163.33

∴ Bobo's standard deviation σ1
= sqrt{{Sigma (x_1 - overline{x}_1)^2}/n} = sqrt{7766.83/6} = 36.0mm

∴ Pa Jiao's standard deviation σ2
= sqrt{{Sigma (x_2 - overline{x}_2)^2}/n} = sqrt{163.33/6} = 5.2mm

OR

You simply set your super duper calculator to SD MODE and for BoBo:

47 DATA
9 DATA
1 DATA
4 DATA
60 DATA
100 DATA

To get Bobo's mean you press x (the one with the overline{x}) on your calculator.
To get Bobo's standard deviation you press σn on your calculator.

SCR CLEAR your data before repeating the above steps for Pa Jiao.

Which method do you think is faster and safer - especially for straightforward non-grouped (i.e. no frequencies) data like the ones in this question?

N.B. Once again, actual buttons might differ in your specific calculator model.

]]> By: Kenny http://www.exampaper.com.sg/questions/e-maths/miss-loi-in-hostage-crisis#comment-13107 Kenny Fri, 05 Sep 2008 17:17:25 +0000 http://www.exampaper.com.sg/questions/e-maths/miss-loi-in-hostage-crisis#comment-13107 Statistics make me dizzy.... Statistics make me dizzy....

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