Here is the design of a clinical trial:

Official Title: Efficacy and Safety of GHX02 in the Treatment of Acute Bronchitis: a Phase 2, Double-blind, Randomized Placebo-controlled Trial

Included conditions:
- Acute Bronchitis

Study Armgroups:
- {'label': 'High-dose GHX02 group(1,920mg/day)', 'type': 'EXPERIMENTAL', 'description': '4 tablets of the GHX02, three times daily for 7 days', 'interventionNames': ['Drug: GHX02']}
- {'label': 'Standard-dose GHX02 group(960mg/day)', 'type': 'EXPERIMENTAL', 'description': '2 tablets of the GHX02 and 2 tablets of the placebo, three times daily for 7 days', 'interventionNames': ['Drug: GHX02', 'Drug: Placebo']}
- {'label': 'Placebo control', 'type': 'PLACEBO_COMPARATOR', 'description': '4 tablets of the placebo, three times daily for 7 days', 'interventionNames': ['Drug: Placebo']}

Interventions:
- {'type': 'DRUG', 'name': 'GHX02', 'description': 'Herbal medicine originating from gualouhengryunhwan', 'armGroupLabels': ['High-dose GHX02 group(1,920mg/day)', 'Standard-dose GHX02 group(960mg/day)']}
- {'type': 'DRUG', 'name': 'Placebo', 'description': 'Placebo tablets', 'armGroupLabels': ['Placebo control', 'Standard-dose GHX02 group(960mg/day)']}

Primary Outcomes:
- {'measure': 'Change in BSS(Bronchitis Severity Score)', 'description': "BSS comprises the sum of five major symptom scores for acute bronchitis: cough, sputum, dyspnea, chest pain during coughing, and rales on auscultation. Each symptom is scored on a 4-point-scale (0=absent, 1=mild, 2=moderate, 3=severe, 4=very severe), with a maximum total score of 20 points. The investigator assesses symptom scores on the basis of the patient's subjective symptoms.", 'timeFrame': 'Day0, Day7'}

Please estimate the sample size based on the assumption: 
The power to detect the difference is 0.8, the two-sided significance level is 0.05, the ratio of allocation of subjects between the groups is 1:1:1, and the dropout rate is 0.2.
Sample size
        The estimated sample size required for this study is 150 patients (50 patients per group).19 The estimation of the number of subjects is based on whether there is a difference in the change from baseline (day 0) to postdose (day 7) Bronchitis Severity Score (BSS), between the control and standard-dose GHX02 group. In an earlier comparable clinical study, the difference was reported to be 2.3, and the SD of the changes in BSS, was estimated to be 3.2.20 The power to detect the difference was assumed to be 0.8, and the two-sided significance level was 0.05. The ratio of allocation of subjects between the groups was 1:1:1, and drop-out rate was presumed to be 0.2.