- * 4. --
* 0.0038 0.0038 mean square error of arith. m a n = * -- = * 0,0014 Vll probableerrorof a single temp. = * 0.6745 X 0.0038 = * 0.0026 probable error of arith. mean = * 0B026 = * 0.00078 */ii
meansquareem of single temp.
l~,X-l~d =
value of K,the bigher the clime cuts the y axis; i. e., the more frequently the arithmetic mean occurs as a value in a set of observations. In Figure 2, the greater the value of h, the steeper the nwes and the less frequent the ocnvrene of large-errors. Thus k is the modulus of precision. (See IVIRLLOR: DD. 51%3.)
.
-(Notie that err- are usually quoted to two ~ W 6 c a nfigures.) t
8. The smallest volume we can use to attain '/lm precision is 20.00'( t0.02). 20.00 cc. of 0.1000 normal KtCfi07isequivalent to 20.00 X 0 . 1 W X 55.84 mg. of iron, or 111.6 mg. This corrrsponds to 1.116 g. of original sample. Notice that to attain the desired precision i t would be necessary to weigh only to the closest mg. 4. The value 0.1032 seems to be in error.
0.1044 0.1040
-
0.1042
A".
The value 0.1032 deviates from the average by 0.0010, which is more than four times the average deviation and can therefore be discarded. The normality of the acid is 0.1042. 6. Figure 1 shows a plot of y = Kc-"" against x with varying values of K. Figure 2 shows a similar plot with k variable; Figure 3 gives the probability NIVS when both hand K are varied. In P i 1, the larger the
-
Av. Dev.
0.W015
f.
-2 0 +x FIGURE 1. (k, mustant: K. vanable)
-x
0
+x
FIGURE 3. (h and K variable).
LAMBDA DELTA LAMBDA LAMBDA DELTA LAMBDA Physical Science Fraternity was organized a t Fairmont State Teachers College, Fairmont, West Va., in 1925 by H.F. Rogers, professor of chemistry, as an honor society for chemistry students. It has since been expanded to include physics and mathematics. Members are elected solely on a basis of scholarship. In 1930 the fraternity was organized on a national basis and since then has established chapters a t the following institutions: Nebraska State Teachers College, Wayne, Nebraska; Western State College, Gunnison, Colorado; State Teachers College, San Diego. California; Nebraska State Teachers College, Keamey, Nebraska; Arkansas State Teachers College, Conway, Arkatlsas; Louisiana State Normal College, Natchitoches, Louisiana; Iowa State Teachers College, Cedar Falls, Iowa; Arizona State Teachers College,
Tempe, Arizona; and Peru State Teachers College, Peru, Nebraska. Only colleges for teachers that are members of the American Association of Teachers Colleges, w other recognized association, such as the North Central Assodation of Colleges and Secondary Schools, are eligible to petition for chapter membership. The fraternity publishes a magazine, The Filter, which contains articles of general scientific interest as well as fraternity news. It is edited by the secretary. The officers of Lambda Delta Lambda are: President, Cleo D. Haught, Fairmont State Teachers College, Fairmont, W. Va.; Vice Prsident, Dr. R. W. Getchell, Iowa State Teachers College, Cedar Falls, Iowa; Secretary, R.Rylaad White, 206 Naomi St., Fairmont, West Va.; and Treasurer,Argyle W. Yost, Farmington, West Va. All communications should be addressed to the secretary.
