Statistics: estimating population size using order statistics

The tutor demonstrates a way to estimate population size from three serial numbers.

Imagine you walk into a room after a convention. The participants had been given, not name tags, but number tags. You find three tags: 21, 225, and 301. Estimate how many people attended.

Solution:

The estimation of N, the population size, is given by

N = ((n+1)*xm/n) – 1, where

n = sample size (3, in this case)

xm = maximum serial number retrieved (301, in this case)

Our result is

N = ((3+1)*301/3) – 1 = 400.33 or 400 people.

Source:

www.ijsr.net

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Math, chemistry: conversion of natural logarithm (ln) to log base 10

The tutor tells a quick hint about calculations with logs.

Although base e log (ln) is often used, some lab scientists prefer base 10 log (aka, common log or simply “log”). Typically, of course, logx is assumed to be base 10. What’s an easy way to convert from lny to logy?

By the change of base formula (see my post here), logab=logb/loga.

Therefore, logy=log10y=lny/ln10=lny/2.303

You’ll sometimes see 2.303 in a chemistry calculation:)

Source:

Mortimer, Charles E. Chemistry, sixth edition. Belmont: Wadsworth, 1986.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Physical chemistry: vapor pressure: why a car may be harder to start in the winter

The tutor implicates the Clausius-Clapeyron equation to explain why combustion is more difficult at lower temperatures.

To burn, a fuel must evaporate.1

In colder temperatures, fuel has less tendency to evaporate. For two specific temperatures (T1 and T2), the Clausius-Clapeyron equation can give a comparison of the vapor pressures (p2 vs p1) of a liquid with molar enthalpy of evaporation ΔHvap:

ln(p2/p1) = ΔHvap(T2 – T1)/(R*T2*T1), where

R = 8.314 J/(K*mol), the idea gas constant.

T1, T2 are absolute temperatures.

Note, from my post from Feb 20, that ΔHvap for gasoline is approximately 38.1kJ/mol.

Example: Compare the vapor pressure of gasoline at 12°C (285K) vs -5°C (268K).

Solution: Let T2 be 268K (-5°C). Then

ln(p2/p1) = 38100(268 – 285)/(268*285) = -1.02

Taking the antilog gives

p2/p1 = 0.36 = 36%

Apparently, gasoline is about 36% as likely to evaporate at -5°C as at 12°C. Not much surprise, really, that a car can be more difficult to start in colder temperatures.

Source:

1Only Vapors Burn 1947 Chemistry of Fire US War Department

Mortimer, Charles E. Chemistry, sixth ed. Belmont: Wadsworth, 1986.

White, J. Edmund. Physical Chemistry, Harcourt Brace Jovanovich College Outline Series. San Diego: Harcourt Brace Jovanovich, 1987.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Dedicated video memory (Adapter RAM): how to see it with OpenGL Extensions Viewer (realtech)

The tutor tells one way to find how much dedicated video memory your system has. This article describes his experience with Windows 7.

In my February 19 post I discuss the difference between adapter RAM (aka dedicated RAM, vRAM, discrete RAM) vs total video memory. I mention therein that, in my (limited) experience, it seems that adapter RAM can be more meaningful in deciding a system’s capability towards a given graphics application.

My son wanted to use Blender at home, so I had to install it. Looking at its requirements, it needs, among other things, compatibility with OpenGL 2.1 and 512MB RAM.

I watched this video about installing Blender; it pointed me to the program OpenGL Extensions Viewer by realtech. (I believe you can find it here.)

After downloading and installing OpenGL Extensions Viewer, it seems to open automatically. If not, then keying OpenGL in the search box will reveal a choice with a pink icon that says GLview; it’s the one to pick. Then, go to Summary: you’ll see Adapter RAM listed:)

Source:

www.blender.org

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Geography, Social Studies: ISIS or ISIL?

The tutor explains two names for the Islamic State, commonly called ISIS.

ISIS and ISIL are two names for the same group. Both are acronyms:

ISIS: Islamic State of Iraq and Syria.

ISIL: Islamic State of Iraq and the Levant.

As I explain in my post from February 4, the Levant refers to the countries along the Mediterranean’s eastern shore: Israel, Jordan, Lebanon, and Syria.

ISIS, or ISIL, presently holds territory in Syria and Iraq.

Apparently, ISIS, or ISIL, is sometimes called simply IS, for Islamic State.

Source:

www.washingtonpost.com

www.aljazeera.com

www.bbc.com

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Chemistry: conversion of Hvap from Btu/gal to kJ/mol for gasoline

The tutor converts, for gasoline, the enthalpy of vaporization from Btu/gal to kJ/mol.

The density of gasoline is approx. 6.25lb/gal; its heat of vaporization is 900Btu/gal. Its molar mass is approx. 114g/mol. Then the conversion is

900Btu/gal x 1gal/6.25lb x 2.2lb/kg x 1kg/1000g x 114g/mol x 1055J/Btu = 38102J/mol = 38.1kJ/mol

Source:

walshcarlines.com

www.rapidtables.com

webbook.nist.gov

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Computer systems: graphics memory: adapter RAM vs total memory

The tutor shares ideas about adapter RAM (aka dedicated RAM, vRAM, discrete RAM) vs total.

Apparently, adapter RAM is physically dedicated to graphics.

In the context of graphics memory, total memory refers to system RAM available for processing graphics. (From my limited observation, it may not include adapter RAM. Rather, it’s the chunk of the computer’s RAM allocated to graphics presentation.)

I don’t have much experience with video RAM, but from what I’ve seen, adapter RAM appears the more meaningful number when considering if a system meets a program’s requirements.

Source:

eHow tech

www.computing.net

www.cnet.com

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Chemistry: a textbook correction

The tutor suggests a correction to example 11.2 in Chemistry (sixth edition) by Charles E. Mortimer.

Example 11.2 (page 275) of said textbook is about the Clausius-Clapeyron equation. At one point, the equation becomes

log(0.526/p1) = 0.491

Then, the antilog is taken; the next line should read

0.526/p1 = 3.10

From there, what follows agrees with the text:

p1 = 0.170

HTH:)

Source:

Mortimer, Charles E. Chemistry, sixth edition. Belmont: Wadsworth, 1986.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

French: verbs: how to form the imparfait

The tutor shows the easy trick to form the imparfait.

Way back in my post from Aug 24, 2012, I mentioned when to use the imparfait vs passé composé vs plus-que-parfait. Today, it’s been brought to my attention that many students might have trouble constructing the imparfait. Here’s how:

  • If the verb is not être, the stem is the present nous form of the verb, without ons. Example: for the verb travailler, the imparfait stem is travaill

The endings, then, are as follows:

pronoun ending
je -ais
tu -ais
elle/il -ait
nous -ions
vous -iez
elles/ils -aient

  • For the verb être, the stem is ét, but the endings are as above.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Spreadsheets: Excel, LibreOffice Calc: number formatting: how to get rid of E-05 (for example)

The tutor explains how to change from scientific notation to regular number format in Excel or LibreOffice Calc.

In my post from Feb 14 I mention that 1.69e-05 equals 0.0000169. Written 1.69e-05, the number is in scientific notation. Perhaps the user is not familiar, or not comfortable with that format – what can be done?

  1. Right-click the cell with the number in scientific notation.
  2. Click Format Cells…
  3. Click Number. There is a click box for the number of decimal places; if the number is in scientific notation with e-05 or such, you’ll likely need lots (maybe 10 or more). There are also choices for how you want the number to appear; select the one desired.
  4. Click OK: Hopefully the number will now be in “ordinary” format.
  5. You may need to widen the column to accommodate the number.
  6. If there is a positive number after the e, the cell contains a large value: for example, 1e+06 is 1 000 000. In such a case, you probably won’t need more decimal places, but might need to widen the column to accommodate the number in regular format:)

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.