# Suggested answer to exercise: Readmission to hospital for asthmatic children, 4

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. Choose , Descriptive Statistics, Crosstabs. Put "Sex" into Row(s): and "Crisis plan" into Column(s):. Click Statistics, Chi-square.

Now we are ready, so Continue, OK.

We get the following output:

Sex * Crisis plan Crosstabulation
Count
Crisis plan Total
Absent Present
Sex Girl 337 77 414
Boy 539 80 619
Total 876 157 1033

Chi-Square Tests
Value   df   Asymp. Sig.
(2-sided)
Exact Sig.
(2-sided)
Exact Sig.
(1-sided)
Pearson Chi-Square 6.199b 1 .013
Continuity Correction a 5.766   1 .016
Likelihood Ratio 6.105   1 .013
Fisher's Exact Test       .013 .009
Linear-by-Linear Association 6.193   1 .013
N of Valid Cases 1033
a. Computed only for a 2x2 table
b. 0 cells (.0%) have expected count less than 5. The minimum expected count is 62.92.

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. We use the independent samples t test with unequal variances to get this.

Click Analyze, Compare Means, Independent Samples T Test. Put "Age (years)", "Hours of wheezing", "Previous admissions", "Pulse (beats/min)", and "Respiration (breaths/min)" into Test variable(s) and "Crisis plan" into Group Variable:. Click Define Groups and put 0 and 1 into the boxes, Continue, OK. We get:

Group Statistics
Crisis plan     N     Mean Std. Deviation Std. Error
Mean
Age (years)
Absent 874 3.7094 3.01660 .10204
Present 157 5.3439 3.76508 .30049
Hours of wheezing
Absent 873 36.1615 67.92851 2.29903
Present 155 43.6387 86.40533 6.94024
Absent 876 2.00 5.732 .194
Present 154 6.73 6.392 .515
Pulse (beats/min)
Absent 869 136.5201 20.86844 .70791
Present 154 133.2532 23.46087 1.89053
Respiration (breaths/min)
Absent 871 44.8875 13.18459 .44674
Present 149 41.2349 12.51561 1.02532

Independent Samples Test
Levene's Test for Equality of Variances t-test for Equality of Means
t df Sig. (2-tailed) Mean Difference Std. Error Difference 95% Confidence Interval of the Difference
F Sig. Lower Upper
Age (years) Equal variances assumed 24.243 .000 -6.003 1029 .000 -1.63457 .27231 -2.16892 -1.10021
Equal variances not assumed -5.151 193.592 .000 -1.63457 .31734 -2.26045 -1.00868
Hours of wheezing Equal variances assumed 5.872 .016 -1.208 1026 .227 -7.47720 6.18925 -19.62223 4.66783
Equal variances not assumed -1.023 189.250 .308 -7.47720 7.31112 -21.89896 6.94457
Previous admissions Equal variances assumed 26.194 .000 -9.265 1028 .000 -4.724 .510 -5.724 -3.723
Equal variances not assumed -8.585 198.625 .000 -4.724 .550 -5.809 -3.639
Pulse (beats/min) Equal variances assumed 3.799 .052 1.756 1021 .079 3.26689 1.86028 -.38352 6.91731
Equal variances not assumed 1.618 198.227 .107 3.26689 2.01872 -.71404 7.24782
Respiration (breaths/min) Equal variances assumed .546 .460 3.148 1018 .002 3.65259 1.16043 1.37548 5.92970
Equal variances not assumed 3.266 208.251 .001 3.65259 1.11842 1.44772 5.85746

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.