Statistics – How to use them when evidencing need Briony Tatem, Public Health Senior Strategic Analysis Officer Introductions

Qualitative vs Quantitative Qualitative research is subjective. It attempts to understand why people behave the way they do and what meaning experiences have for people. Quantitative research is a formal, objective, systematic process in which numerical data is used to obtain information about the world. For example if you wanted to look at older people in an area of Southampton and loneliness, the quantitative data would look at the number of older people in the area and the number of people who live alone and the number of services available. The qualitative data would ask people about how they felt about loneliness, their social networks and how they feel about the level of support available.

Quantitative Data - Statistical Terms Crude rate: A crude incidence/mortality rate is a measure of the number of new cases/deaths due to a disease in a given time span. The crude incidence rate is usually presented as the annual incidence rate and quoted as the number of cases per 100,000 of a defined study population. Directly age-standardised rate: The age-specific rates of the subject population are applied to the age structure of the standard population. This gives the overall rate that would have occurred in the subject population if it had the standard age-profile. Confidence Interval: Informally, a confidence interval indicates a range of values that’s likely to encompass the true value. More formally, the CI around the sample statistic is calculated in such a way that it has a specified chance of surrounding (or “containing”) the value of the corresponding population parameter. http://www.apho.org.uk/resource/item.aspx?RID=48457 Indirect: The age-specific rates of a chosen standard population (usually the relevant national or regional population) are applied to the age structure of the subject population to give an expected number of events. The observed number of events is then compared to that expected and is usually expressed as a ratio (observed/expected). A common example is the standardised mortality ratio (SMR). For indirect you need a whole number not age groups.

Confidence Intervals Significantly different Significantly different Not significantly different? Whilst it is safe to assume that non-overlapping confidence intervals indicate a statistically significant difference, it is not always the case that overlapping confidence intervals do not. A more exact approach is to calculate the ratio of the two estimates, or the difference between them, and construct a test or confidence interval based on that statistic.

Joint Strategic Needs Assessment Key Themes Improving Southampton’s Health Improving economic wellbeing Improving mental health Early years Taking responsibility for health Long term conditions More years, better lives Creating a healthier environment Improving safeguarding Protecting people Whilst it is safe to assume that non-overlapping confidence intervals indicate a statistically significant difference, it is not always the case that overlapping confidence intervals do not. A more exact approach is to calculate the ratio of the two estimates, or the difference between them, and construct a test or confidence interval based on that statistic.

Alcohol-Specific Hospital Admissions – Key Questions Is it an issue in Southampton? What is the trend? Who is affected? Trend data – from this we can see if the problem in Southampton is something new or if an intervention was introduced at a certain point we might be able to see if that has made a difference. Who is affected- this is where we do a deep dive into the subject and see if there are certain areas/groups of people who are affected more than others.

Is it an issue in Southampton? ONS clusters are groups of local authorities that are socioeconomically and demographically similar and hence can represent a more valid comparator group for each district than using the national average.

What is the trend?

Who is affected?

Maps

Qualitative Data Southampton Alcohol Needs Assessment – Structured Interviews: Participants expressed mental health or drug-use as precipitating their heavy alcohol use. Several participants described a sense of community from time spent drinking together. The most common cited barriers to change were being around other drinkers, lack of prescribed drugs to help abstinence and boredom.

Beware bad data: people with an agenda The principle that a person may use deadly force in self-defence if he or she reasonably believes that such force is necessary to prevent imminent death or great bodily harm.

Beware bad data: correlation vs causation The principle that a person may use deadly force in self-defence if he or she reasonably believes that such force is necessary to prevent imminent death or great bodily harm.

Where to find data: DO NOT REFERENCE WIKIPEDIA!!!! Southampton Joint Strategic Needs Assessment: www.publichealth.southampton.gov.uk/HealthIntelligence/JSNA/default.aspx Safe City: http://www.southampton.gov.uk/council-democracy/partnership-working/safe-city.aspx Southampton City Council Surveys: www.southampton.gov.uk/council-democracy/have-your-say/surveys.aspx Public Health England – Fingertips: https://fingertips.phe.org.uk/ Index of Multiple Deprivation: www.gov.uk/government/statistics/english-indices-of-deprivation-2015 NOMIS - Social economic data, population & Census: www.nomisweb.co.uk Office for National Statistics: https://www.ons.gov.uk/ NHS indicator portal: https://indicators.hscic.gov.uk/webview/ The Joint Strategic Needs Assessment (JSNA) is an assessment of the current and future health and social care needs of Southampton’s population: Theme 1: Improving Economic Wellbeing Theme 2: Improving Mental Health Theme 3: Improving Early Years Experience / Better Parenting & Support Theme 4: Taking Responsibility for Health Theme 5: Living with Long Term Conditions (LTCs) & Maximising Quality of Life Theme 6: More Years, Better Lives & End of Life Care Theme 7: Creating a Healthier Environment Theme 8: Improving Safeguarding for Children & Vulnerable Adults Theme 9: Protecting People from Threats to Health

Questions? briony.tatem@southampton.gov.uk