Question: The Western Collaborative Group Study was a prospective study of 3154 healthy men, aged 35-60 years in 1960-61, who were employed in ten participating companies in California. Clinical coronary heart disease (CHD) was diagnosed in 257 men during a follow-up period of approximately nine years. The table below gives the incidence of CHD by five-year baseline age groups.

Do these data demonstrate a significant linear age trend in CHD incidence? Using ptrend, analyze the data and write a summary of your findings that includes a graphical display of the observed CHD trend by age group.