Fascicle II.3 _ Rec. E.427 3 Recommendation E.427 COLLECTION AND STATISTICAL ANALYSIS OF SPECIAL QUALITY OF SERVICE OBSERVATION DATA FOR MEASUREMENTS OF CUSTOMER DIFFICULTIES IN THE INTERNATIONAL AUTOMATIC SERVICE This Recommendation is provided to permit the orderly collection of data required for special studies to identify sources of difficulty in customer use of the international automatic telephone service. When calls are made to points outside a customer's home country, many different sets of ringing and busy tones are encountered. In order to measure the effect of unusual sounding ringing tones and busy tones on customer behaviour, it has been decided to collect data on how long customers listen to such foreign tones as well as to their national tones in order to compare them. The data are to be collected in the same manner as those required for the completion of Table 1/E.422. These data are an extension of those collected for Table 1/E.422, and, as an aid to subsequent analysis, a copy of the current version of that table should be used with the table of this Recommendation. Table 1/E.427 contains questions numbered 1_9. Their relationship to the questions of Table 1/E.422 is shown in parentheses. A preferred set of analyses for identifying the statistical significance of differences between data collected from subscribers when setting up national calls and the corresponding data collected from subscribers when setting up international calls is given below. 1 Determine the percentage change in any measure by use of the formula: Change (Ci) = x 100 j = A, B, C i = 0_2, 2_5 . . ., > 30 where fij is the observed frequency of calls of category i in the country j, Njis the total number of observations in the country j sample, fiH is the observed frequency of calls of category i in the home country H, and NHis the total number of observations in the home country sample. 2 Compare the central location of the distributions by use of the Kruskal_Wallis One_Way Analysis of Variance [1]. 3 Compare the "forms" or "shapes" of the distribution by means of the chi_square test [2]. 4 Compare changes in single valued variables, e.g. percentage incomplete_trunk_code, by use the chi_square test. TABLEAU 1/E.427 (Supplement to Table 1/E.427) Observations of international outgoing telephone calls for quality of service Additionaldetails regarding subscriber dialled calls Outgoing international exchange Group of circuit Period from to Number Percentage Category Subt Tota Subt Tota otal l otal l Details of dialled calls a)b)c) 1. Calls with errors in the dialled number d) 1.1 (6.1) Wrong number dialled . . 100 . 1.1.1 Wrong country code . . . . . . 1.1.2 National trunk prefix (e.g. . . . . "0") wrongly included . . 1.1.3 Wrong trunk code . . . . . . 1.1.4 Wrong subscriber number . . . . . . 1.2 (6.2) Incomplete number dialled . . 100 . 1.2.1 National (significant) number . . . . not dialled or incomplete . . 1.2.2 Trunk code not dialled or . . . . incomplete . . 1.2.3 Subscriber number not dialled . . . . or incomplete . . 2. (5.3) Calls abandonned prematurely . . 100 before receipt of a tone or . (6.3) announcement Interval from end of dialling to disconnecte): 0-5 s . . . . . . 5-10 s . . . . . . 10-20 s . . . . . . 20-30 s . . . . . . 30-50 s . . . . . . > 50 s . . . . . . 3. Post dialling delay on all calls that . . 100 are maintened beyond the start of a tone . or announcement Interval from end of dialling to tone or announcement: 0-5 s . . . . . . 5-10 s . . . . . . 10-20 s . . . . . . 20-30 s . . . . . . 30-60 s . . . . . . 60-90 s . . . . . . > 90 s . . . . . Average excluded portionf) 4. Calls that encounter ringing tonesg) 4.1 (1) Completed calls . . 100 Interval from beginning of tone to answer: 0-10 s . . . . . . 10-20 s . . . . . . 20-30 s . . . . . . 30-50 s . . . . . . > 50 s . . . . . . 4.2 (2.6.4) Incompleted calls . . 100 Interval from beginning of tone to disconnect: 0-10 s . . . . . . 10-20 s . . . . . . 20-30 s . . . . . . 30-50 s . . . . . . > 50 s . . . . . . Number Percentage Category Subt Tota Subt Tota otal l otal l 5. (3-2) . . 100 Calls that encounter busy/congestion . tonesg) Interval from beginning of tone to disconnect: 0-2 s . . . . . . 2-5 s . . . . . . 5-20 s . . . . . . 20-30 s . . . . . . > 30 s . . . . . 6. (4.2) . . 100 Calls that encounter tones that the . observer cannot identify Interval from beginning of tone to disconnect: 0-2 s . . . . . . 2-5 s . . . . . . 5-10 s . . . . . . 10-30 s . . . . . . > 30 s . . . . . 7. (3.3, 4.3)Calls encountering recorded . . 100 announcements . Interval from beginning of announcement to disconnect: 0-2 s . . . . . . 2-5 s . . . . . . 5-10 s . . . . . . 10-30 s . . . . . . > 30 s . . . . . 8. List types of errors in dialling and tone interpretation which could not be categorized p 9. List restrictions on subscriber sampleh) a) The term "calls" throughout this table refers to circuit seizures by outgoing traffic. b) The data for each called country should be collected separately and not combined with other countries. c) The interpretation of these results cannot be made adequately except by comparing them with similar results on national calls. d) The practicability of putting the observation in category 1 will depend upon the observation access point and knowledge of national numbering plan of the outgoing country and of the destination country. e) 0-5 s simplies 0 œ t œ 5. 5-10s simplies 5 < t < 10. f) The "post-dialling delay"measurements may not represent the actuel delay from the time the subscriber finishes dialling to receipt of tone. To the extent that this measurement as observed on the trunk excludes the time from completing of dialling seizure of trunk, the average duration of this excluded time should be reported. g) Identification of tone categories should be made by service observers who are trained to identify the tome categories reliably. h) If access to the trunks being observed is restricted to some specified population of subscribers, e.g., heavy users, non- coin users residents of large urban centres, such restrictions should be noted and reported with the service observations. References [1] MARASCUILO (L. A.), McSWEENEY (M.): Non_Parametric and Distribution_Free Methods for the Social Sciences, Wadsworth Publishing Co., California, 1977. [2] SIEGEL (S.): Non_Parametric Statistics for the Behavioural Sciences, McGraw Hill, New York, 1956.