Question 4: Is the presence of a crisis plan related to other variables which might increase the risk of readmission, such as age, sex, number of previous admissions, pulse rate, or respiration rate? How do children given a crisis plan differ from the other children?

Sex is a qualitative variable, so we will use a cross-tabulation and chi-squared test:

. tab sex crisis, chi2 | crisis plan sex | absent present | Total -----------+----------------------+---------- girl | 337 77 | 414 boy | 539 80 | 619 -----------+----------------------+---------- Total | 876 157 | 1,033 Pearson chi2(1) = 6.1989 Pr = 0.013

Clearly girls are more likely to have crisis plans than boys.

The other variables are all quantitative and, in view of the large sample size, a z test is indicated. In Stata, this is done using a t test with unequal variances:

. ttest age, by(crisis) unequal Two-sample t test with unequal variances ------------------------------------------------------------------------------ Group | Obs Mean Std. Err. Std. Dev. [95% Conf. Interval] ---------+-------------------------------------------------------------------- absent | 874 3.709382 .102038 3.016598 3.509114 3.909651 present | 157 5.343949 .3004859 3.765078 4.750403 5.937495 ---------+-------------------------------------------------------------------- combined | 1031 3.958293 .0994898 3.194535 3.763067 4.153519 ---------+-------------------------------------------------------------------- diff | -1.634567 .3173382 -2.260451 -1.008683 ------------------------------------------------------------------------------ diff = mean(absent) - mean(present) t = -5.1509 Ho: diff = 0 Satterthwaite's degrees of freedom = 193.592 Ha: diff < 0 Ha: diff != 0 Ha: diff > 0 Pr(T < t) = 0.0000 Pr(|T| > |t|) = 0.0000 Pr(T > t) = 1.0000 . ttest wheeze, by(crisis) unequal Two-sample t test with unequal variances ------------------------------------------------------------------------------ Group | Obs Mean Std. Err. Std. Dev. [95% Conf. Interval] ---------+-------------------------------------------------------------------- absent | 873 36.16151 2.299032 67.92851 31.64923 40.67379 present | 155 43.63871 6.940243 86.40533 29.92834 57.34908 ---------+-------------------------------------------------------------------- combined | 1028 37.28891 2.21521 71.02504 32.94206 41.63577 ---------+-------------------------------------------------------------------- diff | -7.477198 7.311123 -21.89896 6.944566 ------------------------------------------------------------------------------ diff = mean(absent) - mean(present) t = -1.0227 Ho: diff = 0 Satterthwaite's degrees of freedom = 189.25 Ha: diff < 0 Ha: diff != 0 Ha: diff > 0 Pr(T < t) = 0.1539 Pr(|T| > |t|) = 0.3077 Pr(T > t) = 0.8461 . ttest admiss, by(crisis) unequal Two-sample t test with unequal variances ------------------------------------------------------------------------------ Group | Obs Mean Std. Err. Std. Dev. [95% Conf. Interval] ---------+-------------------------------------------------------------------- absent | 876 2.003425 .1936601 5.731815 1.623332 2.383517 present | 154 6.727273 .5150541 6.391654 5.709737 7.744809 ---------+-------------------------------------------------------------------- combined | 1030 2.709709 .1891512 6.070544 2.338543 3.080875 ---------+-------------------------------------------------------------------- diff | -4.723848 .550259 -5.808947 -3.638749 ------------------------------------------------------------------------------ diff = mean(absent) - mean(present) t = -8.5848 Ho: diff = 0 Satterthwaite's degrees of freedom = 198.625 Ha: diff < 0 Ha: diff != 0 Ha: diff > 0 Pr(T < t) = 0.0000 Pr(|T| > |t|) = 0.0000 Pr(T > t) = 1.0000 . ttest pulse, by(crisis) unequal Two-sample t test with unequal variances ------------------------------------------------------------------------------ Group | Obs Mean Std. Err. Std. Dev. [95% Conf. Interval] ---------+-------------------------------------------------------------------- absent | 869 136.5201 .7079134 20.86844 135.1307 137.9096 present | 154 133.2532 1.890531 23.46087 129.5183 136.9882 ---------+-------------------------------------------------------------------- combined | 1023 136.0283 .6659108 21.29874 134.7216 137.3351 ---------+-------------------------------------------------------------------- diff | 3.266891 2.018725 -.7140408 7.247824 ------------------------------------------------------------------------------ diff = mean(absent) - mean(present) t = 1.6183 Ho: diff = 0 Satterthwaite's degrees of freedom = 198.227 Ha: diff < 0 Ha: diff != 0 Ha: diff > 0 Pr(T < t) = 0.9464 Pr(|T| > |t|) = 0.1072 Pr(T > t) = 0.0536 . ttest resp, by(crisis) unequal Two-sample t test with unequal variances ------------------------------------------------------------------------------ Group | Obs Mean Std. Err. Std. Dev. [95% Conf. Interval] ---------+-------------------------------------------------------------------- absent | 871 44.88749 .4467426 13.18459 44.01067 45.7643 present | 149 41.2349 1.025318 12.51561 39.20874 43.26105 ---------+-------------------------------------------------------------------- combined | 1020 44.35392 .411634 13.14654 43.54617 45.16167 ---------+-------------------------------------------------------------------- diff | 3.652586 1.118417 1.447716 5.857457 ------------------------------------------------------------------------------ diff = mean(absent) - mean(present) t = 3.2659 Ho: diff = 0 Satterthwaite's degrees of freedom = 208.251 Ha: diff < 0 Ha: diff != 0 Ha: diff > 0 Pr(T < t) = 0.9994 Pr(|T| > |t|) = 0.0013 Pr(T > t) = 0.0006

Age, previous admissions, and respiration are significantly related to the crisis plan.

Children given a crisis plan were more likely to be girls than were other children, and tended to be older, to have had more previous admissions, and to have slower respiration.

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Last updated: 6 February, 2008.