Johnston] 



NAVAHO POPULATION 



211 



95 percent of such values would fall within the range expressed by the 

 observed rate, ±2(rp. The latter range was utilized in connection with 

 the age-specific death rates shown in table 35. 



MEASURES OF AGE DISTRIBUTIONS 



The calculation of the sex ratio score, the male and female age ratio 

 scores, the joint score, and the adjusted joint score, are illustrated in 

 appendix table 1. Given the distribution of a population, by age and 

 sex, the above measures can be caluculated in the following steps : 



AppEJNTDix Table 1. — Illustration of procedure for calculating age and sex ratio 

 scores and joint score for a given age distribution^ 



I Sex ratio score: 



-=6.9 



Male age ratio score: 



141.8 



10.9 



Female age ratio score: — r^ =9.3 



Adjustment for small size of population: 



Joint score: (6.9X3)-|-10.9-|-9.3=40.9 

 Adjusted joint score: 40.9-23.4=17.5 



3500^ 3500 ^ 3500 

 V5'~V22377~149-6 



=23.4 



Step 1. The sex ratio (number of males per 100 females) is cal- 

 culated for each of the given age groups. 



Step 2. The difference between each successive pair of sex ratios 

 is obtained, up to age group YO-74. 



Step 3. The ratio of each successive age group (for each sex sep- 

 arately) to the average of the preceding and succeeding age group is 

 obtained.^ 



* In calculating the age ratios shown in table 28, the above ratio was reversed. Accord- 

 ingly, the male and female age ratios shown in appendix table 1 are obtained by dividing 

 the average of each set of preceding and succeeding age groups by the intervening age 

 group. Either procedure produces the same result. It should be noted, further, that 

 results of sufBcient accuracy can be obtained by using a percentage age distribution instead 

 of the actual numerical frequencies. In calculating the scores given in table 28, percentage 

 age distributions were used exclusively. 



